Wireless communication device, wireless communication terminal and wireless communication method

ABSTRACT

According to one embodiment, a wireless communication device includes: a receiver configured to receive a plurality of first frames each including first information required for uplink multi-user transmission; and a transmitter configured to transmit a second frame generated on the basis of the first information included in the plurality of first frames. The transmitter does not transmit a transmission request for the first information before the first frames are received. The second frame is a frame instructing transmission of a third frame including data after a predetermined time from reception of the second frame.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a Continuation of International ApplicationNo. PCT/JP2016/063504, filed on Apr. 28, 2016, the entire contents ofwhich is hereby incorporated by reference.

FIELD

Embodiments of the present invention relate to a wireless communicationdevice, a wireless communication terminal and a wireless communicationmethod.

BACKGROUND

A communication scheme called OFDMA (Orthogonal Frequency DivisionMultiple Access) where transmissions to a plurality of wirelesscommunication terminals (hereinafter referred to as terminals) orreceptions from a plurality of terminals are simultaneously performed isknown. Particularly, OFDMA where one or a plurality of subcarriers isassigned to a terminal as a resource block and the transmissions to theplurality of terminals or the receptions from the plurality of terminalsare simultaneously performed on the resource block basis is also calledresource-block-based OFDMA. The simultaneous transmissions from a basestation to the plurality of terminals correspond to downlink OFDMAtransmission and the simultaneous transmissions from the plurality ofterminals to the base station correspond to uplink-OFDMA transmission.

A communication scheme called uplink multiuser MIMO (Multiple-InputMultiple-Output) is known where streams are transmitted from theplurality of terminals to the base station by spatial multiplexing(simultaneously by the same frequency band), and the base stationsimultaneously receives these streams by a plurality of antennas.Moreover, a scheme called downlink multiuser MIMO where the streams aretransmitted from the base station to the plurality of terminals byspatial multiplexing (simultaneously by the same frequency band) andeach terminal receiving each stream transmitted to itself is also known.

When uplink OFDMA (UL-OFDMA) or the uplink multiuser MIMO (UL-MU-MIMO:Uplink Multi-User MU-MIMO) communication is to be performed, it may beconsidered that a base station transmits a trigger frame in order toalign the uplink transmission timings of each terminal. By each of theterminals performing transmission after certain time from the receptionof the trigger frame, the transmission timings are aligned whereby theuplink multiple transmission (UL-OFDM or UL-MU-MIMO) is realized. Beforethe transmission of the trigger frame, scheduling includingdetermination of matters required for uplink multiple transmission suchas selection of terminals to be targets of the UL-OFDMA or UL-MU-MIMO orparameter information of the transmission is needed, but since theresource of the communication is limited, the scheduling which canimprove system efficiency as much as possible is in demand. If aterminal not having data to be transmitted is selected as a targetterminal, for example, the communication resources assigned to theterminal are not effectively used in an uplink transmission period, andit is likely that the system efficiency degrades. Moreover, if a basestation tries to collect information from each terminal in advance inorder to efficiently determine the required matters, processing at thebase station becomes complicated, and if a collection period getslonger, it is likely that the system efficiency degrades.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a functional block diagram of a wireless communication deviceaccording to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams explaining an outline of UL-MU-MIMOtransmission and UL-OFDMA transmission.

FIG. 3 is a diagram explaining OFDMA communication and allocation of aresource block.

FIG. 4 is a diagram illustrating a wireless communication groupincluding a base station and a plurality of terminals.

FIGS. 5A and 5B illustrate a basic exemplary format of a MAC frame.

FIG. 6 is a diagram illustrating an exemplary format of an informationelement.

FIG. 7 is a diagram illustrating an operation sequence in accordancewith the present invention.

FIGS. 8A and 8B are a diagram illustrating a format example including anotification information field.

FIG. 9 is a diagram illustrating an example of a format indicatingpresence of a request of UL-MU transmission by each access category.

FIG. 10 is a diagram illustrating a specific operation example ofnotification of presence of data for transmission by each accesscategory.

FIGS. 11A and 11B illustrate a format example of a trigger frame.

FIG. 12 is a diagram illustrating a format example of a physical packetincluding the trigger frame.

FIG. 13 is a schematic configuration diagram of the physical packetUL-MU-MIMO transmitted from a plurality of terminals.

FIG. 14 is a diagram illustrating another example of the operationsequence according to the embodiment of the present invention.

FIG. 15 is a diagram illustrating still another example of the operationsequence according to the embodiment of the present invention.

FIG. 16 is a diagram illustrating a flowchart of an example of anoperation of a terminal according to the embodiment of the presentinvention.

FIG. 17 is a diagram illustrating a flowchart of an example of anoperation of a base station according to the embodiment of the presentinvention.

FIG. 18 is a diagram illustrating a flowchart of another example of anoperation of the base station according to the embodiment of the presentinvention.

FIG. 19 is a functional block diagram of the base station or theterminal according to a second embodiment.

FIG. 20 illustrates an overall configuration example of the terminal orthe base station according to a third embodiment.

FIG. 21 is a diagram illustrating a hardware configuration example of awireless communication device mounted on the base station or theterminal according to the third embodiment.

FIG. 22A and 22B show a perspective view of a wireless communicationterminal in accordance with the embodiment of the present invention.

FIG. 23 is a diagram illustrating a memory card in accordance with theembodiment of the present invention.

FIG. 24 is a diagram illustrating an example of exchange of framesduring a contention period.

DETAILED DESCRIPTION

According to one embodiment, a wireless communication device includes: areceiver configured to receive a plurality of first frames eachincluding first information required for uplink multi-user transmission;and a transmitter configured to transmit a second frame generated on thebasis of the first information included in the plurality of firstframes. The transmitter does not transmit a transmission request for thefirst information before the first frames are received. The second frameis a frame instructing transmission of a third frame including dataafter a predetermined time from reception of the second frame.

Hereinafter, embodiments of the present invention will be described withreference to the drawings. The entire contents of IEEE Std 802.11-2012and IEEE Std 802.11ac-2013, known as the wireless LAN standard and IEEE802.11-15/0132r15 which is a specification framework document directedto IEEE Std 802.11ax as a next generation wireless LAN standard areherein incorporated by reference in the present specification.

First Embodiment

A functional block diagram of a wireless communication device accordingto the first embodiment is illustrated in FIG. 1. This wirelesscommunication device can be implemented in a wireless communication basestation (hereinafter referred to as a base station) or in a wirelesscommunication terminal (hereinafter referred to as a terminal) thatcommunicates with the wireless communication base station. The basestation can be considered as one mode of the terminal since it isdifferent from the terminal in a point that it mainly has a relayfunction but has communication functions basically similar to theterminal in the other points. When a terminal is mentioned in thefollowing explanations, it may refer to a base station as long as theterminal and the base station need not to be particularly discriminatedfrom each other.

In this embodiment, such a case is assumed that uplink multiuser (UL-MU)transmission of at least either one of uplink MU-MIMO (UL-MU-MIMO:Uplink Multi-User MU-MIMO) or uplink OFDMA (UL-OFDMA: OrthogonalFrequency Division Multiple Access) is performed. The base station andthe terminal may have capability of not only the UL-MU (UL-MU-MIMO orUL-OFDMA) but also downlink multiuser (DL-MU) transmission of at leasteither one of downlink MU-MIMO (DL-MU-MIMO) or downlink OFDMA(DL-OFDMA). The UL-MU transmission corresponds to uplink multi-usertransmission, while the DL-MU transmission corresponds to downlinkmulti-user transmission. As the UL-MU transmission, a communicationscheme combining the UL-MU-MIMO and the UL-OFDMA is also applicable andas the DL-MU transmission, a communication scheme combining theDL-MU-MIMO and DL-OFDMA is also applicable.

FIG. 2A illustrates an outline of the UL-MU-MIMO transmission. In theUL-MU-MIMO transmission, the data stream (hereinafter referred to asstream) is transmitted by spatial multiplexing (simultaneously by thesame frequency band) from a plurality of the terminals to the basestation, and the base station receives these streams simultaneously by aplurality of antennas. In the illustrated example, the plurality ofterminals 1 to 4 (STA1 to STA4) transmits the stream simultaneously bythe same frequency band having a width of one channel (here, it isdescribed as a channel M) to an access point (AP) which is the basestation, that is, transmits by spatial multiplexing. The access pointsimultaneously receives these streams and MIMO-demodulates them so as toseparate them into a frame for each terminal.

In the UL-MU-MIMO transmission, since the frame can be transmittedsimultaneously from the plurality of terminals, the system throughputcan be improved. The maximum number of data streams capable ofmultiplexing the UL-MU-MIMO transmission is limited by the number ofantennas of the access point. As an example, when the access point hasfour antennas, the maximum number of streams capable of multiplexing isfour. When each terminal includes one antenna, each can transmit onlyone stream, respectively. It is also possible to transmit a plurality ofstreams by providing a plurality of antennas in one terminal. In thecase of DL-MU-MIMO, a difference is that a communication direction is adirection toward each terminal from the access point. In the DL-MU-MIMO,the stream is transmitted by spatial multiplexing (simultaneously by thesame frequency band) to the plurality of terminals from the basestation, and each terminal receives the stream destined to the terminalitself and decodes it.

FIG. 2B illustrates an outline of the UL-OFDMA transmission. In theUL-OFDMA, one or a plurality of subcarriers is assigned as a resourceblock (may also be called a sub channel, a resource unit, or a frequencyblock) to each terminal, and receptions from the plurality of terminalsare performed simultaneously on the resource block basis. In theillustrated example, the resource block having one or a plurality ofcontinuous subcarriers in continuous frequency domains in one channel(here, described as the channel M) as a unit is assigned to theterminal, respectively, and the receptions are performed simultaneouslyfrom the plurality of terminals. In more detail, the access point (AP)assigns four resource blocks (RB) 1 to 4 included in one channel toplurality of terminals 1 to 4 (STA1 to 4), respectively, and theplurality of terminals 1 to 4 performs transmissions simultaneously bythe resource blocks assigned, respectively. As a result, the UL-OFDMAtransmission is performed from terminals 1 to 4 to the base station. Theresource blocks assigned to each of the terminals are different fromeach other and do not overlap with each other. In the case of DL-OFDMA,a difference is that a communication direction is the direction towardeach terminal from the access point. In the DL-OFDMA, one or a pluralityof subcarriers is assigned as the resource block to each terminal, andthe transmission is performed simultaneously to the plurality ofterminals from the access point on the resource block basis.

The OFDMA will be explained in more detail. FIG. 3 illustrates a statewhere a plurality of channels is arranged in a frequency domain. A guardband is provided between the channels. A band width of one channel is 20MHz, for example. A case where the OFDMA communication is conducted byusing continuous bands of one channel among them (here, the channel M)corresponds to FIG. 2B. In the continuous bands of the channel M (a bandwith a width of 20 MHz, for example), a plurality of subcarriers (52subcarriers, for example, in the case of 20 MHz band) orthogonal to eachother is arranged, and the resource block with one or a plurality ofcontinuous subcarriers as one unit is assigned to terminal 1, terminal2, . . . terminal K (K is an integer of 2 or more. In the example inFIG. 2B, K=4) on the basis of these subcarriers.

The bandwidth of each resource block (or the number of subcarriers) isassumed to be common to each resource block, but different bandwidths(or subcarrier numbers) may be allowed for each resource block.Moreover, regarding the number of resource blocks to be assigned to eachterminal, it is not limited to one resource block per one terminal but aplurality of resource blocks may be assigned to one terminal or thenumber of resource blocks to be assigned to each terminal may bedifferent. If the resource block is constituted by a plurality ofsubcarriers, arrangement of each subcarrier included in the resourceblock may be continuous or discontinuous. A plurality of subcarriersarranged discontinuously may be assigned as the resource block to oneterminal.

In the example in FIG. 3, at least one subcarrier is arranged as a guardsubcarrier between the resource blocks to be assigned to each terminal.The number of the guard subcarriers to be arranged between the resourceblocks may be determined in advance by the system or specification ormay be determined arbitrarily. Moreover, arrangement of the guardsubcarrier between the resource blocks may be not indispensable andnon-arrangement of the guard subcarrier between the resource blocks maybe allowed.

Moreover, the number of channels used in the OFDMA communication is notlimited to 1, but two or more channels may be used for performing theOFDMA communication. At this time, independently for each channel, theresource blocks may be assigned in each channel as described above. Atthis time, assignment of a plurality of resource blocks belonging todifferent channels to one terminal may be allowed. Alternatively,instead of the assignment of the resource blocks independently for eachchannel, a continuous frequency domain being a plurality of channelsbonded may be defined, and the resource blocks may be assigned in thefrequency domain after the bonding. For example, a frequency domain of40 MHz may be defined by connecting two channels each having a width of20 MHz and adjacent to each other in terms of the frequency, theresource blocks may be assigned on the basis of subcarrier groupsorthogonal to each other in the frequency domain of 40 MHz. Similarly, afrequency domain of 80 MHz by connecting four channels or a frequencydomain of 160 MHz by connecting eight channels, each channel having awidth of 20 MHz, may be defined. In this case, the resource blocks onlyneed to be assigned on the basis of the subcarrier groups orthogonal toeach other in the respective frequency domains.

It is assumed here that a terminal that implements OFDMA is capable ofcarrying out reception and decoding (including decoding of errorcorrecting code and demodulation etc.) of a physical packet including aframe on a channel of at least the basic channel width (20 MHz channelwidth if IEEE 802.11a/b/g/n/ac standard-compliant terminal is regardedas a legacy terminal) at the legacy terminal that is to be backwardcompatible. At this time, with regard to the carrier sense, it iscarried out in a unit of the channel. The carrier sense may encompassboth physical carrier sense associated with busy/idle of CCA (ClearChannel Assessment) and virtual carrier sense based on mediumreservation time described in the received frame. As in the case of thelatter, a scheme for virtually determining that a medium is in the busystate, or the period during which the medium is virtually regarded asbeing in the busy state is called a Network Allocation Vector (NAV). Thecarrier sense information based on CCA or NAV carried out in a unit of achannel may be universally applied to all the resource blocks within thechannel. For example, resource blocks belonging to the channel indicatedas being in the idle state by the carrier sense information may beprocessed by universally applying the carrier sense information of thechannel as being in the idle state. The terminal according to thisembodiment is not limited to a terminal performing the carrier sense bya unit of a channel, but performance of the carrier sense (both inphysical and virtual senses) by a unit of a resource block may beallowed as long as a scheme for performing the carrier sense by a unitof a resource block is implemented in the terminal.

With regard to OFDMA, channel-based OFDMA is also possible in additionto the above-described resource-block-based OFDMA. OFDMA of this casemay in particular be called MU-MC (Multi-User Multi-Channel). In MU-MC,a base station assigns a plurality of channels to a plurality ofterminals, and the plurality of channels are simultaneously used tocarry out simultaneous transmissions to the plurality of terminals orsimultaneous receptions from the plurality of terminals. The OFDMA ofthis embodiment which will be described below means theresource-block-based OFDMA: however, an embodiment of channel-basedOFDMA can also be implemented with appropriate replacement of terms andphrases in conformity with the channel-based OFDMA in the followingexplanations such as reading the “resource block” as the “channel”.

A communication scheme (which is called OFDMA & MU-MIMO) that combinesOFDMA and MU-MIMO is also possible. In this communication scheme, aplurality of resource blocks is assigned to a plurality of terminals,respectively, and transmission of MU-MIMO by a unit of a resource blockis performed simultaneously in each of the plurality of resource blocks.Both uplink OFDMA & MU-MIMO and downlink OFDMA & MU-MIMO are possible.When OFDMA or MU-MIMO is mentioned in the following explanations, it maybe read as OFDMA & MU-MIMO.

In the following explanations, a terminal having the capability ofperforming at least either one of UL-OFDMA or UL-MU-MIMO may be calledan UL-MU terminal. A terminal that does not have the capability may becalled a legacy terminal. If the capability of performing UL-MUcommunication can be selectively enabled or disabled, a terminal whosecapability is enabled may be considered as an UL-MU terminal. The UL-MUterminal may further include a capability of performing at least eitherone of DL-OFDMA or DL-MU-MIMO. Moreover, a terminal designated by thebase station as a target of UL-MU communication this time in the UL-MUterminals corresponds to an UL-MU target terminal, while the terminalnot designated by the base station as a target of UL-MU this timecorresponds to an UL-MU non-target terminal.

As illustrated in FIG. 1, a wireless communication device incorporatedin a terminal (which may be either a terminal of non-base station or thebase station) includes upper layer processor 90, MAC processor 10,physical (PHY) processor 50, MAC/PHY manager 60, analog processor 70(analog processors 1 to N), and antenna 80 (antennas 1 to N), where Nrepresents an integer equal to or larger than 1. In the figure, the Nanalog processors and the N antennas are connected in pairs with eachother, but the configuration is not limited to the illustrated one. Forexample, one analog processor and two or more antennas may be connectedto this analog processor in a shared manner.

MAC processor 10, MAC/PHY manager 60, and PHY processor 50 correspond toa mode of a communication processing device or baseband integratedcircuit that carries out processing associated with communications withother terminals (including the base station). Analog processor 70corresponds, for example, to a wireless communication unit or a radiofrequency (RF) integrated circuit that transmits and receives signalsvia antenna 80. The integrated circuit for wireless communication inaccordance with this embodiment may include at least the former of thebaseband integrated circuit (communication processing device) and the RFintegrated circuit. The functions of the communication processing deviceor the baseband integrated circuit may be performed by software(programs) that runs on a processor such as a CPU or may be performed byhardware, or may be performed by both of the software and the hardware.The software may be stored in a storage medium such as a memory deviceincluding a ROM, a RAM, etc., a hard disk, or an SSD and read therefromto be executed. The memory device may be a volatile memory device suchas a DRAM, or a non-volatile memory device such as a NAND or an MRAM.

Upper layer processor 90 is configured to carry out processing for theMedium Access Control (MAC) layer associated with the upper layer orlayers. Upper layer processor 90 is capable of exchanging signals withMAC processor 10. As the upper layer, TCP/IP, UDP/IP, and theapplication layer upper than these two protocols may be mentioned astypical examples but this embodiment is not limited to them. Upper layerprocessor 90 may include a buffer for exchanging data between the MAClayer and the upper layer or layers. It may also be considered that itmay be connectable to a wired infrastructure via upper layer processor90. The buffer may be a memory device, an SSD drive, or a hard disk.When the buffer is a memory device, the memory device may be a volatilememory device such as a DRAM, or a non-volatile memory device such as aNAND or an MRAM.

MAC processor 10 is configured to carry out processing for the MAClayer. As described above, MAC processor 10 is capable of exchangingsignals with upper layer processor 90. Further, MAC processor 10 iscapable of exchanging signals with PHY processor 50. MAC processor 10includes MAC common processor 20, transmission processor 30, andreception processor 40.

MAC common processor 20 is configured to carry out common processing fortransmission and reception in the MAC layer. MAC common processor 20 isconnected to and exchanges signals with upper layer processor 90,transmission processor 30, reception processor 40, and MAC/PHY manager60.

Transmission processor 30 and reception processor 40 are connected toeach other. Also, transmission processor 30 and reception processor 40are each connected to MAC common processor 20 and PHY processor 50.Transmission processor 30 is configured to carry out transmissionprocessing in the MAC layer. Reception processor 40 is configured tocarry out reception processing in the MAC layer.

PHY processor 50 is configured to carry out processing for a physicallayer (PHY layer). As described above, PHY processor 50 is capable ofexchanging signals with MAC processor 10. PHY processor 50 is connectedvia analog processor 70 to antenna 80.

MAC/PHY manager 60 is connected to upper layer processor 90, MACprocessor 10 (more specifically, MAC common processor 20), and PHYprocessor 50. MAC/PHY manager 60 is configured to manage MAC operationand PHY operation in the wireless communication device.

Analog processor 70 includes an analog-to-digital and digital-to-analog(AD/DA) converter and a radio frequency (RF) circuit. Analog processor70 is configured to convert a digital signal from PHY processor 50 intoan analog signal having a desired frequency and transmit it from antenna80, or convert a high-frequency analog signal received from antenna 80into a digital signal. It is considered here that although AD/DAconversion is carried out by analog processor 70, another configurationis also possible according to which PHY processor 50 has the AD/DAconversion function.

The wireless communication device in accordance with this embodiment hasits constituent element (i.e., incorporates) antenna 80 in one singlechip and thereby makes it possible to reduce the mounting area ofantenna 80. Further, in the wireless communication device in accordancewith this embodiment, as illustrated in FIG. 1, transmission processor30 and reception processor 40 shares the N antennas 80. By virtue ofsharing the N antennas 80 by transmission processor 30 and receptionprocessor 40, it is made possible to reduce the size of the wirelesscommunication device of FIG. 1. It is considered here that the wirelesscommunication device in accordance with this embodiment may have aconfiguration different than the one depicted by way of example in FIG.1.

In reception of a signal from a wireless medium, analog processor 70converts an analog signal received by antenna 80 into a baseband signalthat can be processed by PHY processor 50, and further converts thebaseband signal into a digital signal. PHY processor 50 is configured toreceive a digital signal that is received from analog processor 70 anddetect its reception level. The detected reception level is comparedwith the carrier sense level (threshold). When the reception level isequal to or larger than the carrier sense level, PHY processor 50outputs a signal indicative of the fact that the medium (CCA: ClearChannel Assessment) is in the busy state to MAC processor 10 (receptionprocessor 40 to be more precise). When the reception level is less thanthe carrier sense level, PHY processor 50 outputs a signal indicative ofthe fact that the medium (CCA) is in the idle state to MAC processor10(reception processor 40 to be more precise).

PHY processor 50 is configured to carry out decoding processing for thereceived signal (including decoding of error correcting code anddemodulation etc.), processing of removing a physical header (PHYheader) including a preamble, or the like, and extracts a payload.According to IEEE 802.11 standard, this payload is called physical layerconvergence procedure (PLCP) service data unit (PSDU) on the PHY side.PHY processor 50 delivers the extracted payload to reception processor40, and reception processor 40 handles it as a MAC frame. According toIEEE 802.11 standard, this MAC frame is called medium access control(MAC) protocol data unit (MPDU). In addition, PHY processor 50, when itstarted to receive the reception signal, notifies the fact of havingstarted reception of the reception frame to reception processor 40, and,when it completed the reception of the reception signal, notifies thefact of having completed the reception to reception processor 40. Also,PHY processor 50, when the reception signal has been decodedsuccessfully as the physical packet (PHY packet) (when it does notdetect an error), notifies the completion of the reception of thereception signal and delivers a signal indicative of the fact that themedium is in the idle state to reception processor 40. PHY processor 50,when it detected an error in the reception signal, notifies the factthat the error has been detected with an appropriate error code inaccordance with the error type to reception processor 40. Also, PHYprocessor 50, at the timing at which the medium has been determined toenter the idle state, notifies a signal indicative of the fact that themedium is in the idle state to reception processor 40.

MAC common processor 20 performs intermediary processing for delivery oftransmission data from upper layer processor 90 to transmissionprocessor 30 and for delivery of reception data from reception processor40 to upper layer processor 90. According to IEEE 802.11 standard, thedata in this MAC data frame is called medium access control (MAC)service data unit (MSDU). Also, MAC common processor 20 receivesinstructions from MAC/PHY manager 60 and then converts the instructioninto appropriate form of instructions for transmission processor 30 andreception processor 40 and outputs the converted instructions to theseunits.

MAC/PHY manager 60 corresponds, for example, to station managemententity (SME) in IEEE 802.11 standard. In that case, the interfacebetween MAC/PHY manager 60 and MAC common processor 20 corresponds toMAC subLayer management entity service access point (MLME SAP) in IEEE802.11 standard, and interface between MAC/PHY manager 60 and PHYprocessor 50 corresponds to physical layer management entity serviceaccess point (PLME SAP) in IEEE 802.11 wireless local area network(LAN).

It is considered here that although MAC/PHY manager 60 in FIG. 1 isillustrated on the assumption that the functional unit for the MACmanagement and the functional unit for the PHY management are configuredto be integral with each other, these units may be separatelyimplemented.

MAC/PHY manager 60 stores Management Information Base (MIB). The MIBstores various pieces of information such as the capability of thedevice itself and whether various functions are enabled or disabled. Forexample, information may be stored regarding whether or not the terminalitself supports UL-MU-compliant terminal and, if the device itselfsupports UL-MU-compliant terminal, whether or not the function toimplement UL-MU is enabled or disabled. A memory device for storing andmanaging the MIB may be incorporated in MAC/PHY manager 60 or separatelyprovided without being incorporated into MAC/PHY manager 60. When thememory device for storing and managing the MIB is provided separatelyfrom MAC/PHY manager 60, MAC/PHY manager 60 can refer to the separatelyprovided memory device and rewrite rewritable parameters within thememory device. The memory device may be a volatile memory device such asa DRAM, or a non-volatile memory device such as a NAND or an MRAM. Also,storage devices such as a hard disk and an SSD may be used in place ofthe memory device. In the base station, these pieces of information ofthe other terminals that are non-base stations can also be obtained bynotification from these terminals. In that case, MAC/PHY manager 60 isadapted to be capable of referring to and rewriting the informationregarding the other terminals. Alternatively, the memory device forstoring the information on the other terminals may be held and managedseparately from the MIB. In that case, either MAC/PHY manager 60 or MACcommon processor 20 is adapted to be capable of referring to andrewriting the separate memory device. Also, MAC/PHY manager 60 of thebase station may include a grouping function for, when transmittingUL-MU, selecting the terminals to which the resource blocks for UL-MUcommunication are assigned on the basis of various pieces of informationregarding terminals that are non-base stations, or on the basis of therequests from the terminals (i.e., selecting the terminals subject toUL-MU of this time). Also, MAC/PHY manager 60 or MAC processor 10 maymanage the data (transmission) rate applied to the MAC frame and thephysical header aimed at transmission. Also, MAC/PHY manager 60 of thebase station may define a supported rate set which is a rate setsupported by the base station. The supported rate set may includemandatory rates that should compulsorily supported by the terminal thatis connected to the station itself and optional rates.

MAC processor 10 is configured to handle three types of MAC frames,i.e., a data frame, a control frame, and a management frame, and carryout various processing procedures defined in the MAC layer. Here, thethree types of MAC frames are described.

The management frame is for use in management of communication link withanother terminal. As the management frame, for example, a Beacon framemay be mentioned. The Beacon frame notifies attribute andsynchronization information of a group to form a wireless communicationgroup which is a Basic Service Set (BSS) in IEEE 802.11 standard. Also,a frame for authentication or establishing the communication link mayalso be mentioned. It is considered here that a state where a certainterminal completed exchange of information necessary for establishing awireless communication with another terminal is expressed here as (thestate where) the communication link is established. As the exchange ofnecessary information, for example, notification of the functions thatthe device itself supports (for example, support of the UL-MU scheme andvarious capabilities which will be later described, etc.), andnegotiation regarding settings of the scheme may be mentioned. Themanagement frame is generated on the basis of the instruction receivedby transmission processor 30 from MAC/PHY manager 60 via MAC commonprocessor 20.

With regard to the management frame, transmission processor 30 achievesnotifying various pieces of information to other terminals by themanagement frame. A terminal that is non-base station may notify thetype of the terminal itself to the base station by putting in themanagement frame information regarding such as whether it is anUL-MU-compliant terminal, IEEE 802.11n-compliant terminal, or IEEE802.11ac-compliant terminal. As for this management frame, for example,Association Request frame used in the association process which is oneof the procedures for authentication between the terminal and the basestation or Reassociation Request frame used in the reassociation processmay be mentioned. The base station may notify the information on whetheror not it supports UL-MU communication to the terminal that is non-basestation by the management frame. As the management frame used for this,for example, the Beacon frame and a Probe Response frame may bementioned. The Probe Response frame is a response to the Probe Requestframe transmitted by the terminal that is non-base station. The basestation may have a function of grouping terminals which are connected toitself. The above-described notification means at the base station maynotify to each of the terminals a group ID of the assigned group throughthe management frame. As this management frame, for example, Group IDManagement frame may be mentioned. The group ID may be, for example, agroup ID that is defined in IEEE Std 802.11ac-2013. Also, when UL-MUcommunication is performed by the unit of this group, the base stationmay notify necessary information for specifying the resource blocks usedby terminals that belong to this group through an arbitrary managementframe.

Reception processor 40 has a receiver that receives various types ofinformation via the management frame from other terminals. As oneexample, the receiver of the base station may receive informationassociated with compatibility with UL-MU communication from any terminalas a non-base station. Also, it may receive information associated withan adaptable channel width (the maximum available channel width) if thisterminal is a legacy terminal (IEEE 802.11a/b/g/n/ac standard-compliantterminal and the like). The receiver of the terminal may receive fromthe base station information associated with compatibility as to whetheror not UL-MU communication is supported.

The examples of the information to be transmitted and received via themanagement frame as described above are merely examples and variousother types of information can be transmitted and received via themanagement frame between terminals (including the base station). Forexample, an UL-MU-compliant terminal may select either or both of aresource block and a channel that the terminal itself wants to use inthe UL-MU transmission from either or both of non-interference channelsand non-interference resource blocks based on carrier sense. Andinformation regarding the resource block, channel, or both of them thathave been selected may be notified to the base station. In this case,the base station, on the basis of this information, may performassignment of the resource blocks for the UL-MU communication for eachof the UL-MU-compliant terminals. It is considered here that thechannels used in the UL-MU communication may be all of the channels thatare available as the wireless communication system or may be a subset(one or a plurality) of the channels.

The data frame is for use in transmission of data to another terminal ina state where the communication link is established with the otherterminal. For example, data is generated in the terminal by an operationof an application by a user, and the data is carried by the data frame.Specifically, the generated data is delivered from upper layer processor90, via MAC common processor 20, and to transmission processor 30, and aMAC header is added to the Frame Body field, and thus the data frame isgenerated. In addition, a physical header is added to the data frame byPHY processor 50, the physical packet is generated, and the physicalpacket is transmitted via analog processor 70 and antenna 80. Also, whenthe physical packet is received by PHY processor 50, PHY processor 50performs the processing for the physical layer on the basis of thephysical header, and extracts the MAC frame (here, the data frame), anddelivers the data frame to reception processor 40. When receptionprocessor 40 receives the data frame (recognizes that the received MACframe is a data frame), reception processor 40 extracts the informationin the Frame Body field as data, and delivers the extracted data via MACcommon processor 20 to upper layer processor 90. As a result, operationsoccur on applications such as writing, reproduction, and the like of thedata.

The control frame is for use in control in transmission and reception(exchange) of the management frame and the data frame to/from (with) theother wireless communication device. As the control frame, for example,an RTS (Request to Send) frame, a CTS (Clear to Send) frame may bementioned which are exchanged with the other wireless communicationdevice to make a reservation of the wireless medium prior to startingexchange of the management frame and the data frame. Also, as anothercontrol frame, an acknowledgement response frame for confirmation ofdelivery of the received management frame and the data frame may bementioned. As examples of the acknowledgement response frame, an ACK(Acknowledgement) frame and a BA (BlockACK) frame may be mentioned.Since the CTS frame is transmitted as a response to the RTS frame, itcan be said that the CTS is a frame that represents an acknowledgementresponse. A CF-End frame is also one of the control frames. The CF-Endframe is a frame that announces the completion of the CFP (ContentionFree Period) in other words, a frame permitting other wirelesscommunication devices to access the wireless medium. These controlframes are generated by transmission processor 30. With regard to thecontrol frames (the CTS frame, the ACK frame, the BA frame, etc.)transmitted as a response to the received MAC frame, reception processor40 determines whether or not transmission of a response frame (controlframe) is necessary, and outputs information necessary for framegeneration (type of the control frame, information specified in the RAfield, and the like) to transmission processor 30 along with thetransmission instruction. Transmission processor 30 generates anappropriate control frame on the basis of the information necessary forgeneration of the frame and the transmission instruction.

When a MAC frame is transmitted on the basis of CSMA/CA (Carrier SenseMultiple Access with Carrier Avoidance), MAC processor 10 needs toacquire the access right (transmission right) on the wireless medium.Transmission processor 30, on the basis of carrier sense informationfrom reception processor 40, measures the transmission timing.Transmission processor 30, in accordance with the transmission timing,gives the transmission instruction to PHY processor 50, and delivers theMAC frame thereto. In addition to the transmission instruction,transmission processor 30 may instruct a modulation method and a codingmethod to be used in the transmission. In addition to them, transmissionprocessor 30 may provide an instruction regarding the transmissionpower. When MAC processor 10, after having acquired the access right(transmission right), obtained the period of time during which themedium can be occupied (Transmission Opportunity; TXOP), then MACprocessor 10 is allowed to continuously exchange the MAC frames withother wireless communication devices although there is some limitationaccording to such as the QoS (Quality of Service) attribute. The TXOP isacquired, for example, when the wireless communication device transmitsa predetermined frame (for example, an RTS frame) on the basis ofCSMA/CA (Carrier Sense Multiple Access with Carrier Avoidance) andcorrectly receives a response frame (for example, a CTS frame) fromanother wireless communication device. When this predetermined frame isreceived by the other wireless communication device, the other wirelesscommunication device transmits the above response frame after the elapseof the minimum frame interval (Short InterFrame Space; SIFS). Also, as amethod of acquiring the TXOP without using the RTS frame, for example,cases may be mentioned where data frame that requests transmission ofthe acknowledgement response frame is transmitted directly in unicast(as will be described later, this frame may be a frame in the form ofconjunct frames or conjunct payloads) or a management frame thatrequests transmission of the acknowledgement response frame istransmitted, and acknowledgement response frame (ACK frame, BlockACKframe or the like) in response thereto is correctly received.Alternatively, when a frame is transmitted that does not request, forthe other wireless communication device, transmission of theacknowledgement response frame with a period equal to or longer than thetime period needed to transmit this frame specified in the Duration/IDfield (hereinafter referred to as Duration field) of this frame, then itmay be interpreted that with the transmission of this frame, TXOP of theperiod described in the Duration field has been acquired.

Reception processor 40 is configured to manage the above-describedcarrier sense information. The carrier sense information is managed foreach channel, for example. This carrier sense information includes bothphysical carrier sense information regarding busy/idle states of themedium (CCA) input from PHY processor 50 and virtual carrier senseinformation on the basis of the medium reservation time described in thereceived frame. If either one of these carrier sense information piecesindicates the busy state, then the medium is regarded as being in thebusy state in which transmission is prohibited. It is considered herethat in IEEE 802.11 standard, the medium reservation time is describedin the Duration field in the MAC header. MAC processor 10, when havingreceived a MAC frame that is addressed to other wireless communicationdevices (that is not addressed to the device itself), determines thatthe medium is virtually in the busy state from the end of the physicalpacket including this MAC frame over the medium reservation time. Ascheme of this type for virtually determining that a medium is in thebusy state, or the term during which the medium is virtually regarded asbeing in the busy state is called Network Allocation Vector (NAV). Itcan be said that the medium reservation time represents the length oftime period during which suppression of accesses to the wireless mediumis instructed, i.e., the length of time period during which accesses tothe wireless medium are deferred.

Here, the data frame may be a frame such that a plurality of MAC framesare conjunct with each other or payload portions of a plurality of MACframes are conjunct with each other. The former data frame is called A(Aggregated)-MPDU and the latter data frame is called A(Aggregated)-MSDU (MAC service data unit) in IEEE 802.11 standard. Inthe case of the A-MPDU, a plurality of MPDUs are conjunct with eachother within the PSDU. Also, in addition to the data frame, themanagement frame and the control frame are also eligible for thisconjunction. In the case of the A-MSDU, MSDUs which are a plurality ofdata payloads are conjunct with each other within the frame body of oneMPDU. In both cases of the A-MPDU and the A-MSDU, delimiter information(length information, etc.) is stored in the data frame such that theconjunction of the MPDUs and combination of MSDUs can be appropriatelyseparated by the terminal on the reception side. Both of the A-MPDU andthe A-MSDU may be used in combination. Also, the A-MPDU may involve nota plurality of MAC frames but one single MAC frame, and also in thiscase the delimiter information is stored in the data frame. Also, whenthe data frame is an A-MPDU or the like, responses to the plurality ofMAC frames are transmitted together. The BA (BlockACK) frame is used asthe response in this case in place of the ACK frame. In the followingexplanations and figures, the notation of MPDU may be used, but it isassumed here that this notation includes not only the single MAC framebut also the cases of the above-described A-MPDU and the A-MSDU.

According to IEEE 802.11 standard, several procedures are defined inmultiple stages to be taken for a terminal that is non-base station toparticipate in a BSS (which is called Infrastructure BSS) configuredwith the base station amongst others and to perform exchange of dataframes within the BSS. For example, there is provided a procedure calledassociation, according to which an Association Request frame istransmitted from the terminal that is non-base station to the basestation to which the terminal requests the connection. The base station,after having transmitted an ACK frame for the association request frame,transmits an Association Response frame which is a response to theassociation request frame.

The terminal stores the capability of the terminal itself in theassociation request frame and transmits this association request frame,and thus can make notification of the capability of the terminal itselfto the base station. For example, the terminal may add, to theassociation request frame, the channel, the resource (resource block orstream), or both of them that the terminal itself can support, andinformation for identifying the standard supported by the terminalitself into the association request frame and transmit this associationrequest frame. This information may be also set in the frame transmittedby the procedure called reassociation (reassociation) to reconnect toanother base station. In this procedure, a Reassociation Request frameis transmitted to the other base station to which reconnection isrequested from the terminal. The other base station, after havingtransmitted the ACK frame in response to the reassociation requestframe, transmits a reassociation response which is a response to thereassociation request frame.

As the management frame, in addition to the association request frameand the reassociation request frame, a beacon frame, a probe responseframe, etc. may be used. The beacon frame is basically transmitted bythe base station, and is capable of storing parameter notifying thecapability of the base station itself along with the parametersindicating the attributes of the BSS. In view of this, as the parameternotifying the capability of the base station itself, the base stationmay be adapted to add the information on whether or not UL-MUcommunication is supported. Also, as the other parameter, information onthe supported rates of base station may be notified. The supported ratesmay include mandatory rates and an optional rate. The probe responseframe is a frame transmitted from the terminal that transmits the beaconframe in response to a probe request frame received. The probe responseframe is basically the one that notifies the same content as that of thebeacon frame, and the base station, when it uses the probe responseframe, is also capable of notifying the capability of the station itself(whether or not UL-MU communication is supported, supported rate and thelike) to the terminal that transmitted the probe request frame. Bymaking this notification to the UL-MU-compliant terminal, an operationmay be performed according to which the terminal, for example, enablesthe function of the UL-MU communication of the terminal itself.

It is considered here that the terminal may notify the informationregarding the rates available on the device itself from among thesupported rates of the base station rate as the information fornotifying the capability of the device itself to the base station.Meanwhile, it is considered that with regard to the mandatory rates fromamong the supported rates, a terminal that is connected to the basestation has the capability of executing the mandatory rates.

It is considered here that if notification of other piece or pieces ofinformation among the pieces of information mentioned above makes it toessential of the piece or pieces of information, then notification ofthe other piece or pieces of information may be omitted. For example,suppose a case where a terminal is always an UL-MU-compliant terminal ifa capability that is compliant with a new standard or specifications isdefined and as long as the terminal is compliant with that capability orspecifications, notification of the fact that the terminal is anUL-MU-compliant terminal does not need to be explicitly performed.

FIG. 4 illustrates a wireless communication system in accordance withthis embodiment. This system includes a base station (AP: Access Point)100 and a plurality of terminals (STA: STAtion) 1 to 8. The BSS (BasicService Set) 1 is formed by base station 100 and terminals 1 to 8operating under base station 100. This system is a wireless LAN systemcompliant with IEEE 802.11 standard using CSMA/CA (Carrier SenseMultiple Access with Carrier Avoidance). It is considered here thatlegacy terminals (IEEE 802.11a/b/g/n/ac standard-compliant terminals,etc.) other than the terminals (UL-MU terminals) in accordance with thisembodiment may exist within BSS 1.

FIG. 5A illustrates the basic exemplary format of the MAC frame. Thedata frame, the management frame, and the control frame in accordancewith this embodiment are based on a frame format of this type. Thisframe format basically includes the fields of MAC header, Frame body,and FCS. The MAC header includes, as illustrated in FIG. 5B, the fieldsof Frame Control, Duration/ID (called simply Duration in some cases),Address 1, Address 2, Address 3, Sequence Control, QoS Control, and HT(High Throughput) Control.

These fields do not need to always exist and there may be cases wheresome of these fields do not exist. Also, any field or fields that arenot illustrated in FIG. 5 may exist. For example, an Address 4 field mayfurther exist. Also, a notification field (or may be called a controlfield) as will be described later may exist in the MAC header as a fieldor a subfield.

The field of Address 1 indicates Receiver Address (RA), the field ofAddress 2 indicates Transmitter Address (TA), and the field of Address 3indicates either BSSID (Basic Service Set IDentifier) (which may be thewildcard BSSID whose bits are all set to 1 to cover all of the BSSIDsdepending on the cases) which is the identifier of the BSS, or TA,depending on the purpose of the frame.

As described above, two fields of Type and Subtype are set in the FrameControl field. The rough classification as to whether it is the dataframe, the management frame, or the control frame is made by the Typefield, and fine discrimination of more specific types among the roughlyclassified frames, for example, as to whether it is a BA frame, a BARframe, or a beacon frame within the control frame is made by the Subtypefield.

The Duration/ID field describes the medium reservation time as describedabove, and it is determined that the medium is virtually in the busystate from the end of the physical packet including this MAC frame tothe medium reservation time when a MAC frame addressed to anotherterminal is received. The scheme of this type to virtually determinethat the medium is in the busy state, or the period during which themedium is virtually regarded as being in the busy state, is, asdescribed above, called NAV (Network Allocation Vector). The QoS fieldis used to carry out QoS control to carry out transmission with thepriorities of the frames taken into account. The HT Control field is afield introduced in IEEE 802.11n and exists when the Order field in theframe control field is set to 1 in the QoS data frame or the managementframe. The HT Control field can be extended to VHT (Very HighThroughput) Control field of IEEE 802.11ac or to HE (High Efficiency)Control field of IEEE 802.11ax which is the next generation wireless LANstandard and is capable of making notification according to variousfunctions of IEEE 802.11n, IEEE 802.11ac or IEEE 802.11ax, respectively.

In the management frame, an information element (Information element;IE) to which a unique Element ID (IDentifier) is assigned is set in theFrame Body field. One or a plurality of information elements may be setin the Frame Body field. The information element has, as illustrated inFIG. 6, the fields of an Element ID field, a Length field, and anInformation field. The information element is discriminated by theElement ID. The Information field is adapted to store the content of theinformation to be notified, and the Length field is adapted to store thelength information of the information field. The notification field(control field) which will be described later may be set to a Body fieldof the management frame. In this case, the notification field may have aformat of the information element.

Frame check sequence (FCS) information is set in the FCS field as achecksum code for use in error detection of the frame at the receptionside. As an example of the FCS information, CRC (Cyclic Redundancy Code)may be mentioned.

FIG. 7 illustrates an exemplary operation sequence of the base station(AP) 101 and a plurality of terminals including the terminals (STAs) 1to 4 in accordance with this embodiment. The plurality of terminalsincluding terminals 1 to 4 is UL-MU-compliant terminals. Though theterminals other than terminals 1 to 4 are not shown in the figure,actually, the other terminals 5 to 8 may exist as illustrated in FIG. 4.

In the figure, a short section indicated by a solid line with bilateralarrows represents short interframe space (SIFS). However, the sectiongiven reference character T1 indicates SIFS or another certain time(IFS). Sections 501A, 503A, and 505A indicated by bold arrows representa total (carrier sense time or standby time) of DIFS/AIFS[AC] time andCSMA/CA backoff time. However, SIFS and DIFS/AIFS[AC] time are onlyexamples, and it may be another time (IFS) as long as it is certain timedetermined in advance. It is considered here that the DIFS/AIFS [AC]time refers to either the DIFS time or the AIFS [AC] time. When it isnot QoS-compliant, the DIFS/AIFS [AC] time refers to the DIFS time. Whenit is QoS-compliant, the DIFS/AIFS [AC] time refers to the AIFS [AC]time which is defined in accordance with the access category (AC) (to belater described) of the data to be transmitted.

In this exemplary operation sequence, under a circumstance thatcommunications are performed with the basic channel width (or a bandwidth connecting a plurality of channels) individually between the basestation and the individual terminals including terminals 1 to 4, thebase station determines start of UL-MU (UL-OFDMA or UL-MIMO)transmission. When the base station determines the start of the UL-MUtransmission, it transmits a trigger frame (a physical packet includingthe trigger frame to be more precise) 507 which becomes a trigger of theUL-MU transmission, and terminals 1 to 4 transmit the data frames(physical packets including the data frames to be more precise) 509,510, 511, and 512 after certain time T1 from reception of the triggerframe. As a result, the UL-MU transmission from terminals 1 to 4 to thebase station is carried out. In contrast with the UL-MU communication,communication carried out individually with the basic channel width (ora band width connecting a plurality of channels) between the individualterminals and the base station is called single user communication insome cases. Hereinafter, this sequence will be described to be moreprecise.

Before the UL-MU transmission is started, the normal single usercommunication is carried out between the base station 101 and theindividual terminals including terminals 1 to 4. That is, when the datafor uplink transmission is held in terminal 1, terminal 1 measures theCCA value by carrying out the carrier sense during the carrier sensetime (standby time) of the DIFS/AIFS[AC] and a randomly determinedbackoff time in order to acquire the access right to the wirelessmedium, and when it has been determined that the medium (CCA) is in theidle state, terminal 1 acquires the access right to transmit, forexample, one frame. Terminal 1 transmits a data frame (morespecifically, a physical packet including the data frame) 501 includingthe data to be transmitted and when the base station has received thisdata frame 501 successfully, then the base station returns an ACK frame(more specifically, a physical packet including the ACK frame) 502 whichis an acknowledgement response frame after the elapse of SIFS time aftercompletion of reception of data frame 501. Terminal 1 upon reception ofACK frame 502 determines that the transmission of data frame 501 hasbeen successful.

It is considered here that the data frame to be transmitted to the basestation may be an aggregation frame (A-MPDU, etc.), and theacknowledgement response frame by which the base station responds may bea BA frame (this also applies to the following explanations).

Terminal 2 similarly acquires the access right and transmits data frame503, and the base station transmits ACK frame 504 after the elapse ofthe SIFS time after completion of reception of data frame 503. Terminal3 also acquires the access right and transmits data frame 505 similarly,and the base station transmits ACK frame 506 after the elapse of theSIFS time after completion of reception of data frame 505. Theillustrated examples illustrate the case where only terminals 1 to 3transmit the data frames to the base station, but terminal 4 and theterminals 5 to 8, not shown, may carry out frame exchange similarly.Also, in the illustrated examples, the communication is conducted in theorder of terminal 1, terminal 2, and terminal 3, but this is only anorder of acquiring the access right, and the communication may beconducted in any order.

Here, in data frames 501, 503, 505, etc. to be transmitted to the basestation, each terminal sets notification information (may also be calledcontrol information) that the base station requires in UL-MU in anotification field (control field). That is, the data frame has a roleof transmitting the notification information required for UL-MU inaddition to a role of transmitting the above-described data to the basestation. In other words, the data frame includes information(above-described data) with a purpose different from that of thenotification information in the Frame Body field. The notificationinformation may be set to data frames transmitted in UL-MU in additionto the data frames to be single-user transmitted.

Examples of the notification information include information relating topresence of a request of UL-MU transmission, information relating topresence of data for which UL-MU transmission is desired, informationrelating to a data type of the data for which UL-MU transmission isdesired and the like. Moreover, information relating to a data amount ofdata for which UL-MU transmission is desired (a number of pieces or asize of the data or both) is also included. Moreover, a desiredcommunication scheme (communication scheme of OFDMA or MU-MIMO) is alsoincluded. Moreover, a desired resource (a resource block for OFDMA and astream for MU-MIMO) or a number of resources according to thecommunication scheme may be also included. The desired resource may bespecified by a resource number or a stream number or may be specified bythe other methods. Moreover, information of an occurrence cycle of datain the terminal may be also included. Moreover, a value of communicationdelay allowable by the application (allowable delay) can be included.The notification information may include at least one of the informationin the examples described here or may include information of a type notdescribed here. The notification information is spontaneouslytransmitted from the individual terminals in a state where atransmission request for the notification information from the basestation is not made. That is, the individual terminals transmit thenotification information in a form joining in a frame to be transmittedin the normal single user communication. Moreover, as described above,when a plurality of frames (data frames, etc.) are UL-MU transmittedfrom a plurality of terminals, notification information for each of theterminals can be set to the respective frames and transmitted in a formjoining in the frames. In this case, notification information fordetermining matters required for the subsequent UL-MU transmission canbe transmitted during the UL-MU transmission. Details of the contents ofthe notification information will be described later.

Here, the notification field in which the notification information isset may be provided as a new field in the MAC header as illustrated inFIG. 8A. Alternatively, a reserved area in the existing field (fielddefined by the existing standard) may be used as the notification field.Moreover, the notification field may be provided in the physical headeras illustrated in FIG. 8B or a reserved area in the existing field inthe physical header may be used as the notification field. Moreover, thenotification field may be set not in the MAC header but in a Body fieldof the frame. If the data frames to be transmitted to the base stationconstruct an A-MPDU, for example, one of the plurality of MAC frames ismade the management frame, and the Frame Body field of the managementframe may carry the notification field. At this time, the notificationfield may specifically have the information element format as previouslyillustrated in FIG. 6, where an element ID may be newly assigned to theinformation element in which the notification field is set. Moreover, anew value may be defined to the frame including the notification fieldas a subtype of the Frame Control field. An information element of thenotification field may be additionally set in the frame body of theexisting management frame. The specific format of the notification fieldrelies on the contents of the notification information to be set.

Here, the notification information to be notified by each terminal inthe notification field will be explained. As described above, thenotification information is used for the base station to carry outscheduling including determination of required matters of UL-MU and thelike.

As a first example of the notification information, information relatingto presence of a request for UL-MU transmission can be cited. When thereis remaining data to be transmitted to the base station is present in atransmission buffer (transmission queue) , it can be considered thatthere is a request for UL-MU transmission. As a format example of thenotification information, it may be set by using 1 bit such that in thecase of bit 1, there is a request for UL-MU transmission, while in thecase of bit 0, there is no request for UL-MU transmission.Alternatively, a bit relationship may be opposite to this. When the basestation is to select a target terminal of the UL-MU transmission, it mayselect them from the terminals having the requests for UL-MUtransmission. As a variation, a more data field in the Fragmentationfield used for notifying presence of remaining data for downlink to someterminal in a power-save mode may be used also as the notificationinformation of the first example. Presence of transmission data may benotified by setting the bit of the more data field to 1, for example.There can be such a method that the notification field itself is notprovided if there is no request for UL-MU transmission.

There can be a case where the terminal has data to be transmitted to thebase station but it wants to transmit by single user transmission, notby the UL-MU transmission. Since the plurality of terminals share theresource (one channel width band, for example) in the UL-MUtransmission, a frame length (physical packet length) in transmission ofthe same data size becomes longer than that in the single usertransmission in which one terminal can use one channel band width. Whenthe frame length becomes longer, a possibility of failure intransmission (possibility that a frame error is detected on thereception side) becomes higher. Thus, there can be a situation that theterminal wants to conduct the single user transmission, not the UL-MUtransmission, if reliable transmission is desirable. In such a case, theterminal only needs to set information indicating that there is notransmission request (there is no remaining data) in the notificationfield and to carry out single user transmission of the data as usual onthe CSMA/CA basis.

As a second example of the notification information, it may beinformation for specifying presence of a request for UL-MU transmissionfor each data type (that is, presence of data for UL-MU transmission foreach data type) in the terminal. The data type may be IEEE 802.11standard TID (Traffic ID: traffic type) or AC (Access Category). In thefollowing, AC will be basically described as the data type, but TID maybe used instead (the same applies to explanations for a third or laterexample of the notification information).

As a priority control scheme using the access category (AC), EDCA(Enhanced Distributed Channel Access) is known. EDCA will be explainedbriefly. In the wireless LAN based on IEEE 802.11 standard, when data isdelivered from an upper layer (LLC layer or the like) to the MAC layer,in the case where the terminal is compliant to QoS (Quality of Service),a traffic type (TID) is notified together with the data. The terminalscompliant to the existing standards such as IEEE 802.11n or IEEE802.11ac are compliant to QoS.

The data is classified into four ACs on the basis of the traffic type,for example. As an example, values of TID are 0 to 15, and 0 to 7 areused by the terminal (including the base station) in the EDCAenvironment, while 8 to 15 are used by the terminal (including the basestation) in the HCCA (hybrid coordination function (HCF) controlledchannel access (HCCA)) environment or in the HEMM (HCCA, EDCA mixedmode) environment. Here, the EDCA environment is assumed, and the datais classified into any one of four ACs in accordance with the value ofTID which is any one of 0 to 7.

As for the AC types, BACKGROUND (AC_BK), BEST EFFORT (AC_BE), VIDEO(AC_VI), and VOICE (AC_VO) are defined. Transmission buffers(transmission queues) are provided for the four ACs, respectively, andthe classified data is stored in the applicable transmission buffer. Thetransmission buffer (transmission queue) may be a memory device or maybe an SSD, a hard disk and the like. If the transmission buffer is amemory device, the memory device may be a volatile memory device such asa DRAM or may be a non-volatile memory device such as a NAND or an MRAM.

An EDCA parameter is determined for each AC, and this parameterdetermines a difference in priority in a medium access in transmission.As an example of the parameter, AIFS[AC] and a minimum value CWmin and amaximum value CWmax of a Contention Window (CW) can be cited. AIFS[AC],CWmin and CWmax are set to smaller values for the AC with the higherpriority of a medium access. The other examples of the parameter includeTXOP limit which is an upper limit value of TXOP.

In the terminal, the procedure for data transmission based on CSMA/CA isindependently carried out for each AC having data for transmission. Thatis, the carrier sense is carried out during a waiting time includingAIFS[AC] and the backoff time for each AC, and the AC whose waiting timereaches zero for the first time acquires the access right. When there isa plurality of AC whose waiting time has become zero at the same time,the AC with higher priority in medium access acquires the access right.The backoff time (random time) is obtained by multiplying an integerselected randomly from the Contention Window (CW) by a slot time. Aninitial value of CW is given by CWmin and the value of CW is incrementedup to CWmax at each re-transmission.

FIG. 9 illustrates an example of a format indicating presence of arequest for UL-MU transmission (presence of data for UL-MU transmission)for each AC. 1 bit is provided for each of BACKGROUND (AC_BK), BESTEFFORT (AC_BE), VIDEO (AC_VI), and VOICE (AC_VO). It can be configuredthat bit 1 is set when there is data in a transmission queue applicableto each of these ACs, while bit 0 is set when there is no data.Alternatively, a bit relationship may be opposite to this. In thisexample, four bits are needed in order to represent presence of data fortransmission of each AC.

FIG. 10 illustrates a specific operation example of notification ofpresence of data for transmission in each AC by using a format in FIG.9. A transmission queue is provided for each AC, and there is one MSDU(may be also MPDU, PSDU or PPDU, etc.) in the transmission queue ofAC_VO. Two MSDUs are present in the transmission queue of AC_VI, no MSDUis present in the transmission queue of AC_BK, and one MSDU is presentin the transmission queue of AC_BE. A size of each MSDU does not have tobe the same and the size of MSDU is different depending on the AC in theillustrated example. Assume that a procedure compliant to CSMA/CA isstarted simultaneously and independently in each AC at transmission, thewaiting time of AC_VO first becomes zero, and it acquires the accessright. In this case, the first MSDU in the transmission queue of AC_VOis read, and the transmission queue becomes empty. A Body field of theMAC frame is generated on the basis of the read MSDU, and by adding theMAC header to the Body field, a MAC frame is generated. At this time,information indicating presence of remaining data for transmission isset for each AC in the notification field of the MAC header. Since thetransmission queue in AC_VO is empty, bit 0 is set to an applicablesubfield, since MSDU (two pieces) is present in the transmission queuein AC_VI, bit 1 is set to an applicable subfield, since the transmissionqueue in AC_BK is empty, bit 0 is set to an applicable subfield, andsince there is MSDU (one piece) in AC_BE, bit 1 is set to an applicablesubfield, respectively. The generated MAC frame is transmitted to thebase station in TXOP based on the acquired access right. In theillustrated example, an acknowledgement response frame (BA frame or ACKframe, etc.) is received by terminal 1 from the base station afterelapse of SIFS time after the transmission of the MAC frame.

In the existing IEEE 802.11 standard, when bit 1 is set in the more datafield in the Frame Control field of the MAC header in the MAC frame(beacon frame, etc.) transmitted by the base station, it is interpretedthat there is still data in the same access category (AC) in the basestation, but it leads to a problem that a state of the transmissionqueue in the other ACs cannot be notified to the terminal. On the otherhand, since the state of the transmission queue in a plurality of ACscan be notified by the notification information in the second example,the base station can efficiently carry out UL-MU communication.

As a third example of the notification information, a priority oftransmission (discriminated from the priority of the above-describedmedium access) may be set for each AC. The priority of “high”, “medium”,and “low” may be set for each AC, for example. The priorities in thenumber smaller than or larger than three may be defined. If there is nodata for transmission, the transmission priority may be set to “low”, orpriority “none” or the like indicating that there is no data fortransmission may be defined separately. The notification information maybe defined by combining this third example with the second example. Inthis case, presence of data for transmission and the priority oftransmission are set for each AC.

As a fourth example of the notification information, AC which has datamost desirable to transmitted among the plurality of ACs (AC_VO, AC_VI,AC_BK, and AC_BE), that is, AC with the highest transmission prioritymay be designated. In this case, in order to designate one of these fourACs, 2 bits are needed. It may be so designated, for example, “00” forAC_VO, “01” for AC_VI, “11” for AC_BK, and “10” for AC_BE. Thenotification information may be defined by combining this fourth examplewith the second example. In this case, bits representing presence ofdata transmission (4 bits, for example) and bits designating one AC inthis example (2 bits, for example) are needed for each AC.

As a fifth example of the notification information, it may beinformation for specifying a data amount for transmission for each ofall or some ACs. The data amount may be a number of pieces of datapresent in the transmission queue in each AC (here, it is assumed to beMSDU but it may be PPDU or other PDU or SDU) or a size of each MSDU orboth of them. Alternatively, it may be a total data size of MSDUremaining in the transmission queue. Moreover, it may be a time length,not the size. Other than those described here, it may be anything aslong as it is information that can specify the data amount. Whentransmission is to be carried out by transmission by an aggregationframe (A-MPDU or A-MSDU, etc.), for example, it may be information onhow many aggregation frames are present. A quantizing method inexpressing the data amount may be an arbitrary method. It may be assumedthat a basic unit is 32 μs which is a time length, and the data amountmay be expressed by integer times of 32 μs, for example. At this time,if a field length for setting the data amount is 8 bits, 32 μs to 8160μs can be expressed, for example. The 32 μs is an example, and a timelength with another size may be also used as a basic unit. Moreover, 8bits are also an example, and a field length with another length may bealso used. Moreover, as another quantizing method, it may be assumedthat the basic unit is 4096 octets which is a size, and the data amountmay be expressed by integer times of 4096 octets. It may be soconfigured that, when the field length for setting the data amount is 4bits and a value of the field is 1, it expresses 4096 octets, and in thecase of 2, it expresses 8192 octets or the like. When an actual dataamount does not match integer times of 4096 octets, a value larger thanand the closest to the actual data amount may be employed. If the valueof the field is 15, it may indicate that the data amount is larger than57344 octets. The 4096 octets are an example, and another size may beused as a basic unit. Moreover, the 4 bits are also an example, and afield length with another length may be also used.

As a sixth example of the notification information, it may beinformation for specifying a data amount (not for each AC) for overalltransmission in the terminal. Specifically, a number of pieces of thedata for transmission (here, it is assumed to be MSDU but it may be PPDUor other PDU or SDU) remaining in the transmission buffer (transmissionqueue) or a size of each MSDU or may be the both. Alternatively, it maybe a total size of the MSDU remaining for transmission or may beinformation other than described here. Moreover, it may be a timelength, not the size. Other than those described here, it may beanything as long as it is information that can specify the data amount.When transmission is to be carried out by transmission by an aggregationframe (A-MPDU or A-MSDU, etc.), for example, it may be information onhow many aggregation frames are present. A quantizing method inexpressing the data amount may be an arbitrary method. It may be assumedthat a basic unit is 32 μAs which is a time length, and the data amountmay be expressed by integer times of 32 μs, for example. At this time,if a field length for setting the data amount is 8 bits, 32 μs can beexpressed, for example. The 32 μs is an example, and a time length withanother size may be also used as a basic unit. Moreover, 8 bits are alsoan example, and a field length with another length may be also used.Moreover, as another quantizing method, it may be assumed that the basicunit is 4096 octets which is a size, and the data amount may beexpressed by integer times of 4096 octets. It may be so configured that,when the field length for setting the data amount is 4 bits and a valueof the field is 1, it expresses 4096 octets, and in the case of 2, itexpresses 8192 octets or the like. When an actual data amount does notmatch integer times of 4096 octets, a value larger than and the closestto the actual data amount may be employed. If the value of the field is15, it may indicate that the data amount is larger than 57344 octets.The 4096 octets are an example, and another size may be used as a basicunit. Moreover, the 4 bits are also an example, and a field length withanother length may be also used.

As a seventh example of the notification information, it may beinformation for specifying a TXOP length required for the subsequenttransmission for all or some ACs. The TXOP length may be expressed, byassuming that the basic unit is 32 μ, by integer times of 32 μs, forexample. At this time, if a field length for setting the TXOP length is8 bits, 32 μs to 8160 μs can be expressed, for example. The 32 μs is anexample, and a time length with another size may be also used as a basicunit. Moreover, 8 a bits are also an example, and a field length withanother length may be also used. Instead of the TXOP length, a dataamount required for the subsequent transmission may be used for each ofall or some ACs. The data amount may be a data length of PPDU or MSDU,etc. An expressing method of the data amount is similar to thenotification information in the fifth or sixth example. Here, theinformation for specifying the TXOP length or the data amount requiredfor the subsequent transmission is explained for each AC but it may beinformation for specifying the TXOP length or the data amount requiredfor the subsequent transmission in the terminal, not for each AC.

As an eighth example of the notification information, it may beinformation on which of OFDMA and MU-MIMO (may be MU-MIMO&OFDMA asdescribed above. The same applies to the following) the terminal wantsto use. If the terminal is compliant to only either one of thecommunication schemes and it has already notified the base station ofthe communication scheme to which the terminal itself is compliantduring an association process or the like, notification of thisinformation may be omitted.

As a ninth example of the notification information, it may beinformation specifying a desired resource (a resource block in OFDMA anda stream in MU-MIMO) or information expressing the resource number orboth of them in compliant to the UL-MU communication scheme (OFDMA orMU-MIMO). Specification of the desired resource may be made by aresource number or a stream number or may be made by another method. Asan example of another method, the desired resource may be specified bydesignating a range of resource numbers. When there are resource numbers1 to 8, for example, the range may be designated such as “resourcenumbers 6 to 8”. At this time, a plurality of ranges may be designated.

The various types of notification information illustrated in theabove-described first to ninth examples are used singularly and also maybe used in arbitrary combination as long as it does not cause conflict.The notification information may be defined by combining both the firstexample and the second example, for example. Three or more pieces of thenotification information may be also combined. The first to ninthexamples are only exemplification and information other than them can bealso used as the notification information. Information indicating anoccurrence cycle of data in the terminal may be used, for example. Theoccurrence cycle may be information for each AC or for each TIDdescribed above. Alternatively, it may be information indicating a valueof communication delay (allowable delay) allowable in the application ofthe terminal. Moreover, information relating to TSPEC (TrafficSpecification) defined by IEEE 802.11 standard (average data rate, MSDUlength, minimum physical rate, etc.) may be transmitted as notificationinformation. When a plurality of pieces of the notification informationis to be transmitted, they may be transmitted in one frame or may bedivided into a plurality of frames in transmission.

Here, a part of or the whole of the notification information may be setby using an existing field such as QoS Control field. At this time, areserved area in the existing field may be used, or when the existingfield has a plurality of pattern formats, a pattern may be newly definedfor setting the notification information so that the notificationinformation is set in the new pattern format. A value of the existingfield itself may be used as the notification information. For example,the format of the QoS Control field is different in accordance with thesubtype of the Frame Control field, but a TID subfield and a TXOPDuration Requested subfield are included as an example. In the TIDsubfield, TID of the data currently being transmitted is set, and avalue required as the subsequent TXOP is set in the TXOP DurationRequested subfield. The values of these subfields may be used as thenotification information.

The base station manages a state of each terminal by storing thenotification information notified from each terminal in the notificationfield in an internal storage device and by managing the notificationinformation of each terminal. As described above, notification of thenotification information in the notification field includes a case wherethe existing field is used. The base station determines execution of theUL-MU transmission at arbitrary timing, at timing determined in advanceor at timing when a condition determined in advance is satisfied or thelike. As the timing determined in advance, it may be by each certainbeacon interval cycle or may be other timings. As the conditiondetermined in advance, it may be presence of a certain number or more ofthe terminals which request UL-MU transmission or it may requiresatisfaction of a predetermined criterion by a radio wave situation(busy rate, usage or any other indexes). It is only necessary for thebase station to determine execution of the UL-MU transmissionindependently of reception of the data frame transmitted in single-userfrom terminals 1 to 4.

When the base station determines execution of UL-MU transmission, itdetermines matters required for the UL-MU transmission. Target terminalsof UL-MU transmission are selected, for example. As a selecting method,selection may be made from the terminals which have the requests forUL-MU transmission. At this time, the selection may be made from theterminals having data for transmission of a specific data type (AC orTID, etc.). Alternatively, the target terminal may be selected on thebasis of the data amount or the TXOP length or the data amount requiredfor the subsequent transmission such that the terminal with the largestdata amount of the specific data type or the largest TXOP length or thedata amount required for the subsequent transmission is selected withpriority, or the terminal with substantially the same data amount or thesame TXOP length or the same data amount required for the subsequenttransmission is selected (details will be described later).Alternatively, the terminal may be selected on the basis of the priorityin transmission of a specific data type such as the terminal with thehighest priority in transmission of the specific data type.Alternatively, the terminal belonging to the same group may be selectedwhen the base station groups the terminals. Alternatively, as a standardfor selecting a group, an item of presence of a request for UL-MUtransmission, a data amount of a specific data type or priority or thelike for each terminal belonging to each group may be considered. Theselection may be made on the round-robin basis or may be made in arandom manner. Alternatively, the selection method may be a method ofselecting terminals having data with the same or close size as that ofthe data to be transmitted or a method of selecting terminals having thesame or close occurrence cycle of data (terminals having the occurrencecycle included within a certain value or terminals having the closestpredetermined number of the occurrence cycles) or the like.Alternatively, when a propagation path response with each terminal isgrasped in advance, a combination of terminals with small spatialcorrelation (small interference) may be selected. The number ofterminals to be selected should be within a range of the maximummultiplexing number or less according to the communication scheme. Inthe case of OFDMA, it is selected within a range of the maximumavailable resource block number or less and in the case of MU-MIMO, itis selected within the maximum available spatial resource number(maximum stream number) or less. A lower limit of the terminal numbersto be selected is determined, and the number of the terminals at thelower limit or more may be selected.

Moreover, the base station carries out assignment of resources to beused in UL-MU transmission to the selected target terminals. Theresources are resource blocks (one or a plurality of subcarriers) in thecase of OFDMA and spatial resource (streams) in the case of MU-MIMO. Inthe assignment of resources, the resources are assigned so as not to beoverlapped between the target terminals. When usable resources aredetermined in advance for each terminal (for example, when determined atassociation with the base station or at arbitrary timing after that orwhen the usable resources are determined in accordance with thecapability of the terminal or the like), the resources determined inadvance are assigned. In the processing of selecting the target terminaldescribed above, the target terminals may be selected so that the usableresources are not overlapped between the terminals by considering theresource usable in each terminal.

Other than selection of the target terminals and assignment of theresources described above, other parameter information to be specifiedto the target terminals may be determined. As an example, the basestation may determine a PPDU length transmitted by the target terminalin common. When notification information including a TXOP length or adata amount required for the subsequent transmission or the both isreceived from the target terminal, for example, the PPDU length may bedetermined by using the TXOP length or the data amount (PPDU length orthe like) notified from the target terminal. The PPDU length may bedetermined on the basis of the terminal having the longest TXOP or thedata amount among the target terminals, for example. Details will bedescribed along with explanation for generating a trigger frame.

In selection of the target terminal, assignment of the resources, anddetermination of other parameter information, when the notificationinformation has been notified from the terminal through the existingfield, the base station may carry out scheduling by using theinformation stored in the existing field.

When execution contents of UL-MU communication such as the targetterminals of the UL-MU communication, the resources to be assigned tothe target terminals or the like are determined, the base stationgenerates trigger frame 507.

Here, trigger frame 507 may be defined on the basis of the format of ageneral MAC frame illustrated in FIG. 5. As an example, it may be soconfigured that a type of the Frame Control field is a value indicatinga control frame and a value of a subtype is a value newly defined forthe trigger frame. However, the frame type of the trigger frame is not acontrol frame but configuration that it is a management frame or a dataframe is not excluded. Moreover, a value in the existing standard may beused for the value of the subtype. Information required as a role oftrigger frame 507 may be added as an information element to the FrameBody field of the existing management frame, for example.

The RA (receiver address) of trigger frame 507 may be a broadcastaddress or a multicast address and the address may be set in the address1 field as an example. Moreover, TA (transmitter address) may be a MACaddress or a BSSID of the base station.

In the Frame Body field of the trigger frame, terminal informationfields (STA Info. Fields) are set according to the number of targetterminals in UL-MU transmission as illustrated in FIG. 11A. In asequence example in FIG. 7, since terminals 1 to 4 are selected, fourterminal information field (STA info fields) 1 to 4 are set. Informationto be individually notified to the terminal is set in each terminalinformation field. An example of the information to be set in theterminal information field is shown below.

As an example, an identifier of the selected terminal is set in theterminal information field. The identifier of the terminal may be a MACaddress of the terminal, an association ID (AID) or any other unique IDsbetween the terminals. Moreover, parameter information individually usedby the terminal in UL-MU transmission may be set in the terminalinformation field. Examples of the parameter information are shownbelow.

As an example of the parameter information, at least one of a datalength allowed for transmission, an error correcting code scheme, and anMCS (Modulation and Coding Scheme) prescribing transmission rate of PHYor MAC or the both of them may be used. The data length may be aphysical packet length or when the physical header length is fixed, itmay be a MAC frame length or a MSDU length or may be a length of anotherportion. A unit of the data length may be a data size or a time length(occupied time length in a space). The data length may be common to eachterminal or differences among terminals may be allowed. A maximum valueof the data length (PPDU length or the like) may be determined inadvance by a standard or a system and in this case, the data size isspecified within a range of the maximum value.

When the base station determines the data length (PPDU length, forexample), it may estimate or calculate the largest PPDU length among thetarget terminals, for example, and may set the largest PPDU length as adata length of uplink transmission.

Alternatively, when the base station selects the target terminals, itmay select terminals having the same or close PPDU length to each otheron the basis of the PPDU length required by the terminals. When the PPDUlength to be transmitted is different depending on the terminals, aftercompletion of the transmission of the terminals with a short of PPDUlength, a waste is caused in the resource assigned to the terminal withthe short of PPDU length until completion of transmission of theterminal with a longer PPDU length, which might cause deterioration ofsystem efficiency. Thus, by selecting the terminals with a close PPDUlength, the system efficiency can be improved.

Moreover, the base station may determine an MCS of each target terminaland specify information of the MCS in the terminal information field sothat the PPDU length of each target terminal carrying out UL-MUcommunication becomes equal or close to each other. Even in the case ofthe same data size, for example, the occupied time length is differentif the applied MCS is different. Thus, when the data size of eachterminal is different, the occupied time length of PPDU of each terminalmay be brought to the same or close to each other by adjusting the MCS.Regarding the MCS, in addition to the MCS applied to the MAC frame, ifthe

MCS can be specified to a part of or all of the fields of the physicalheader, the MCS may be specified to the field of the physical header.

As another example of the parameter information, information of a datatype to be transmitted by each terminal may be designated. As the datatype, information of an access category (AC) or traffic information(TID: Traffic ID) may be set. The designated data type may be differentfor each terminal or may be common to the terminals. Moreover, aplurality of data types may be designated to one terminal.

As still another example of the parameter information, informationrelating to the UL-MU communication scheme may be designated. When amechanism that the base station designates either of OFDMA or MU-MIMOand causes the terminal to carry out UL-MU transmission is employed, forexample, information designating either of the OFDMA or MU-MIMO isdesignated. The terminal carries out the UL-MU transmission in acommunication scheme designated by the trigger frame. In this case, thebase station may obtain the communication scheme which can be handled byeach terminal in the association process with the terminal or anarbitrary timing after that and select the target terminals from theterminals compliant to the communication scheme to be used.

Moreover, as still another example of the parameter information,information designating one or a plurality of resources assigned to theterminal may be set in the terminal information field in accordance withthe communication scheme of UL-MU to be used. In the case of UL-OFDMA,for example, the information designating one or a plurality of resourceblocks assigned to the terminal may be set in the terminal informationfield. A format of the information designating the resource block may beany format as long as it can specify the resource block. Designation maybe made by a number of the resource block, for example. The designationmay be made by the number in the order of the resource block from a highfrequency side or from a low frequency side. In the case of theUL-MU-MIMO transmission, information designating streams assigned to theterminal such as information of patterns of preambles (preambles forestimating propagation path response) to be added to a frame may bedesignated as an example. At this time, the preambles of each terminalare assumed to be selected to be orthogonal between the terminals(details will be described later). In the case of the UL-MU-MIMOtransmission, the number of streams allowed for each terminal may bedesignated. The number of streams that can be handled by each terminalis assumed to have been obtained by the base station in advance ascapability information of the terminal.

In a Frame Body field of the trigger frame, a common information fieldfor notifying information (Common Information) common to the targetterminals may be provided separately from the terminal information fieldas illustrated in FIG. 11B. In the common information field, informationto be notified in common to the target terminals is set. When thetransmission data size to be designated to each terminal is common, forexample, it may be set to the common information field, not in theterminal information field. The UL-MU communication scheme to be usedmay be set not in the terminal information field but in the commoninformation field. Moreover, when a group is selected as a plurality ofthe target terminals, a group ID of the group may be designated in thecommon information field. At this time, when all the terminals belongingto the group are the target terminals, setting of identifiers of theindividual terminals in the terminal information field may be omitted.However, it is assumed that each terminal grasps what number of theterminal information fields is assigned to the terminal itself has beennotified from the base station in advance.

Here, the example in which the terminal information field and the commoninformation field are set in the Frame Body field is illustrated, but apart of or the whole of the information to be set in the terminalinformation field and the common informant field may be arranged in theMAC header. Moreover, a part of or the whole of the information to beset in the terminal information field and the common information fieldmay be arranged in the physical header as illustrated in FIG. 12. Thephysical header in FIG. 12 includes L-STF (Legacy-Short Training Field),L-LTF (Legacy-Long Training Field), L-SIG (Legacy Signal Field), thecommon information field, and the terminal information field. Theterminal information field includes a field for the number of terminals.L-STF, L-LTF, and L-SIG are fields that can be recognized by a legacystandard such as IEEE 802.11a, and information such as signal detection,frequency correction, transfer speed and the like is stored. When allthe required information is set to the terminal information field or thecommon information field in the physical header or to both of them, theterminal information field and the common information field may beomitted from the MAC frame.

Terminals 1 to 4 which received trigger frame 507 from the base stationand are designated by trigger frame 507 transmit data frames 509, 510,511, and 512 including the data for uplink transmission (to be moreprecise, the physical packets including the data frames) to the basestation after certain time T1 from completion of the reception oftrigger frame 507. The transmission of data frames 509 to 512 is carriedout by using the resource (resource block or spatial resource(corresponding to a preamble pattern)) designated by trigger frame 507.The transmission timings of the data frames transmitted by terminals 1to 4 are synchronized with each other, and as a result, data frames 509to 512 transmitted from terminals 1 to 4 are transmitted by frequencymultiplexing or spatial multiplexing. When there is no data to betransmitted to the base station, terminals 1 to 4 may transmit a framein a format determined in advance, that is, Null Packet, for example.The Null Packet refers to a frame without a Body field. Alternatively,it may be so configured that terminals 1 to 4 do not transmit anythingwhen there is no data to be transmitted to the base station. When thebase station receives the Null Packet or it does not receive anything,it may be so determined that the terminal has no data to transmit.

Here, the certain time T1 in FIG. 7 may be SIFS (Short Inter-frameSpace) time (=16 μs) which is a time interval between the frames definedin the MAC protocol specification of IEEE 802.11 wireless LAN as anexample or may be longer than that. A value of the certain time T1 isstored in the common information field, and terminals 1 to 4 may obtainthe value of the certain time T1 from the common information field.Besides, the certain time T1 may be notified in advance by anothermethod such as a beacon frame or other management frames.

When there is a condition designated in the terminal information fieldand the common information field, terminals 1 to 4 generate and transmitdata frames (to be more precise, generation and transmission of aphysical packet including a data frame) so that the condition issatisfied.

When information of an access category (AC) to be transmitted by eachterminal is designated by trigger frame 507, for example, data belongingto the designated AC (hereinafter referred to as designated AC) (it isassumed to be MSDU, here) is selected, and a data frame including theMSDU is transmitted. When the data frame to be transmitted can include aplurality of SDUs in the data frame such as an aggregation frame, orwhen a plurality of resources is designated and the MSDU can betransmitted for each resource or when there is no MSDU belonging to thedesignated AC, the MSDU belonging to AC other than the designated AC(hereinafter referred to as non-designated AC) may be included. At thistime, how many MSDUs are to be selected from the designated AC and thenon-designated AC, respectively, or which AC in the non-designated AC isto be selected may be determined by an arbitrary method. As an example,at least one MSDU belonging to the designated AC may be selected, whileMSDU may be selected from each AC freely other than that. When the AC isdesignated by trigger frame 507, the above-described function of EDCA(function of transmission by the AC which acquires the access right thefastest by carrying out the procedure of CSMA/CA independently by eachAC) does not have to be carried out for the time being, or a parameterof EDCA may be forcedly set to a predetermined value so as to controlsuch that the AC can acquire the access right reliably.

Moreover, when a condition relating to the data length such as the PPDUlength is designated by trigger frame 507, the data frame is generatedand transmitted so that the condition of the data length is satisfied.When the PPDU length does not satisfy the designated value, for example,padding data may be added to the end of the MAC frame or for the time ofshortage, no data may be transmitted (null data may be transmitted).When the MCS is designated by the trigger frame, the target terminalapplies the designated MCS and generates the MAC frame or the physicalpacket.

The base station receives data frames 509 to 512 (to be more precise,the physical packets including the data frames) transmitted fromterminals 1 to 4 by OFDMA or MU-MIMO. In the case of OFDMA, the dataframes transmitted from terminals 1 to 4 are received by the respectiveresource blocks, while in the case of MU-MIMO, the data frame of eachterminal is received from each stream. When the base station correctlyreceives the data frame transmitted from each terminal, it transmits anacknowledgement response frame 513 to terminals 1 to 4 after elapse ofSIFS time from reception of each data frame. The SIFS time is an exampleand it may be time defined separately (IFS).

As the transmission of acknowledgement response frame 513, for example,the BA frame is transmitted by the resource block by which respectivedata frame was received for each of the terminals. When the data frametransmitted to the base station includes not an A-MPDU but aconventional (single) MPDU, an ACK frame may also be used in place ofthe BA frame (it is considered here that it is possible to return a BAframe in the case of a conventional MPDU). In this manner, transmissionof the BA (or ACK) frames in respective resource blocks for each of theterminals corresponds to transmission of the acknowledgement responseframes in downlink OFDMA. In this case, each terminal receives the BA(or ACK) frame by its own resource block (reception filters are set suchthat the signals can be received in this manner in units of the resourceblocks). Alternatively, simultaneous transmission of the BA frame (orACK frame) is possible for each terminal through each stream,respectively. That is, the acknowledgement response frames aretransmitted in downlink MU-MIMO. The downlink MU-MIMO is defined by IEEE802.11ac. It is not excluded, either, that the uplink transmission isOFDMA and the downlink transmission is MU-MIMO or the uplinktransmission is MU-MIMO and the downlink transmission is OFDMA.

Alternatively, a single frame that includes all of the acknowledgementresponses for terminals 1 to 4 may be transmitted (single usertransmission). In this case, this frame may be called a Multi-STA BAframe. As a specific configuration, for example, Multi-TID BA framedefined by IEEE 802.11 standard may be diverted. As one example, the BAinformation fields of the Multi-TID BA frame are arranged in the numberequal to the number of the terminals and the identifier of the terminal(for example, AID (Association ID) or part of the AID) is set in thereserved field in the TID information subfield of each BA informationfield. Values of the Block Ack Starting Sequence Control subfield andBlock Ack Bitmap subfield of the of each BA information field should beset in a conventional manner in accordance with data frames 509 to 512which the acknowledgement responses should be returned. A multicastaddress of the group to which all of terminals 1 to 4 belong or thebroadcast address should be set in the RA (receiver address) of theMulti-STA BA frame. By this setting, the BA can be notified to aplurality of terminals by one single frame. Also, a new value may bedefined for the Subtype of the Frame Control field.

In addition, when ACK frames are returned to terminals 1 to 4 instead ofBA frames, identifiers of the terminals are set in some fields of thereserved fields within the TID information subfield of each BAinformation field, and a part of the remaining fields of the reservedfields are enabled (set bit(s) to 1 (s)). In addition, when this bit isor these bits are enabled, the Block Ack Starting Sequence Controlsubfield and the Block Ack Bitmap subfield are omitted (do not exist).By virtue of this, ACKs of the plurality of terminals can be notified tothe terminals by one single frame. The examples described herein aremerely examples and existing frames other than the Multi-TID BA framemay be diverted, or a new frame may be defined without diverting theexisting frames.

Here, the case where acknowledgement response frame 513 is transmittedto terminals 1 to 4 at once is illustrated, but a method of returning aBA frame or an ACK frame to terminals 1 to 4 in turn is also possible.When returning sequentially, such operations may be carried out in orderthat the BA frame is returned to the first terminal after completion ofreception of the data frame which was uplink-transmitted to and from thesecond terminal onward, a BAR frame is transmitted, and the BA frame istransmitted as its response. Alternatively, from the second terminalonward, such operations may be repeated in order that the BA frame istransmitted without transmission of the BAR frame, and the ACK frame isreceived as a response. Which terminal is the first may be notified inthe common information field or the terminal information field, etc. oftrigger frame 507 or may be notified by another method. When beingnotified by trigger frame 507, implicit notification may be made thatthe terminal to which the first terminal information field is assignedis the first terminal or the like. The notification may be made by amethod other than those described here.

After the transmission of the acknowledgement response frame 513, UL-MUtransmission by terminals 1 to 4 and transmission of the acknowledgementresponse frame(s) by the base station may be carried out repeatedly.

As described above, a preamble for estimating a propagation pathresponse of uplink may be added to the header of the physical packet tobe UL-MU-MIMO transmitted by terminal 1, 2, 3, and 4. At this time, thepreambles for the terminals are made to be orthogonal to each other. Tobe orthogonal means that an inner product of vectors having each valueof a bit string in the preamble as a component becomes zero.

FIG. 13 illustrates outline configuration of a physical packet to beUL-MU-MIMO transmitted by terminals 1 to 4. In the header of eachphysical packet, fields such as preambles 1 to 4 and the like arearranged other than L-STF, L-LTF, and L-SIG. The same value is set ineach terminal in the fields of L-STF, L-LTF, L-SIG and the like beforepreambles 1 to 4. That is, information required for each terminal hasbeen notified in advance from the base station so that the same value isset or it is determined in advance by the system or by the standard orboth. The letter “L” in L-STF, L-LTF, and L-SIG represents a “legacy”,and these fields are fields that can be recognized even by legacyterminals.

In the fields after preambles 1 to 4 (including the data field in whichthe MAC frame is stored), different contents (or may be the samecontents) are set for each terminal. In the base station, the fieldsafter preambles 1 to 4 are spatially separated between the terminals byusing preambles 1 to 4. The base station may designate preamble patternsorthogonal to each other among terminals 1 to 4 in terminal informationfields 1 to 4 in the notification frame.

The base station calculates propagation path information of the uplinkbetween the antenna of each of terminals 1 to 4 and the plurality ofantennas in the base station by using preambles 1 to 4 and decodes thefield of each terminal after preambles 1 to 4 by using the calculatedpropagation path information. A field storing information relating to anMCS (Modulation and Coding Scheme) of each data field or the like may beseparately arranged after preambles 1 to 4 in the header of the physicalpacket.

In a sequence example in FIG. 7, in terminals 1 to 4, the notificationfield in which the notification information is set is provided in thedata frame, but the notification field may be provided in the managementframe, for example. It may be an association request frame transmittedin the association process with the base station, may be anauthentication request frame or may be any other types of the managementframe. Moreover, provision of a notification field in the control frameother than the data frame and the management frame is not excluded.Moreover, as described above, the notification field in which thenotification information is set may be provided not in a frame subjectedto the single-user transmission but in a frame for the UL-MUtransmission.

In the sequence example in FIG. 7, since the notification informationhas been transmitted by a frame (to be more precise, a physical packetincluding a frame) subjected to single-user transmission at an arbitrarytiming from individual terminal to the base station, a large time gapmay be caused between timing when the base station receives thenotification information and timing when the base station determinesstart of UL-MU transmission. That is, long time can elapse fromtransmission of the last notification information by the terminal to thebase station until the UL-MU communication is started. In this case,data for transmission may be no longer present in the terminal due to anoperation of an application on the terminal side, time-out, orcompletion of data transmission by the single-user transmission. If suchterminal is designated as the target terminal by the trigger frame, theresource (resource block or spatial resource (corresponding to thepreamble pattern)) assigned to that terminal is wasted. Thus, when startof the UL-MU communication is determined, the base station may providean inquiry phase before the transmission of the trigger frame so as toinquire whether there is a request for the UL-MU transmission from eachterminal and select the target terminals from the terminals having theUL-MU transmission request. At this time, the terminals to be inquiredon whether they have UL-MU transmission requests may be terminals whichtransmitted that they have UL-MU transmission requests in thenotification information or transmitted the information that can specifythat they have the request. As a result, the number of terminals to beinquired can be narrowed down and thus, an inquiry period can bereduced. Moreover, since a possibility of inquiry to a terminal nothaving an UL-MU transmission request is reduced, efficient inquiry canbe realized.

FIG. 14 illustrates an example of an operation sequence of the inquiryphase carried out before transmission of the trigger frame. Before theinquiry phase, it is assumed that single-user communication is beingcarried out between the individual terminals and the base station as inbefore the transmission of the trigger frame in FIG. 7.

As illustrated in FIG. 14, when the base station determines start ofUL-MU transmission, it determines a candidate terminal of the UL-MUtransmission and transmits inquiry frame 531 to one of the candidateterminals (terminal 1, here). Terminal 1 transmits request frame 532including information indicating presence of a request for UL-MUtransmission after elapse of SIFS time from reception of inquiry frame531.

Inquiry frame 531 and request frame 532 may be defined on the basis of aformat of the general MAC frame illustrated in FIG. 5. The inquiry framemay be any one of the types of control frame, management frame, and dataframe. As an example, the inquiry frame is a control frame. A value of asubtype may be newly defined for inquiry frame 531. The RA of inquiryframe 531 is a MAC address of terminal 1, and the TA is a BSSID or a MACaddress of the base station. However, the RA may be given a broadcastaddress or multicast address, and an identifier of terminal 1 (AID orMAC address, etc.) may be set in the Frame Body field. If there is acondition for the UL-MU communication fixed at the current point of time(a communication scheme, for example) in the Frame Body field or thelike, the condition may be set.

Request frame 532 may be any one of the types of control frame,management frame, and data frame. As an example, request frame 532 is acontrol frame. A value of a subtype may be newly defined for requestframe 532. Request frame 532 includes information for specifyingpresence of a request for UL-MU transmission. As an example, a bitindicating presence of data for UL-MU transmission may be provided in aMAC header, a Body field or a physical header. Moreover, Request frame532 may include the above-described notification information (see thefirst to ninth examples), and in this case, the latest notificationinformation can be transmitted immediately before start of the UL-MUcommunication.

The base station also makes selection in order for the other candidateterminals and repeatedly carries out sets of transmission of an inquiryframe and reception of a request frame. In the illustrated example,inquiry frame 533 is transmitted to terminal 2 after terminal 1, andrequest frame 534 is received from terminal 2 after the SIFS time. Then,after the SIFS time from the reception of request frame 534, inquiryframe 535 is transmitted to terminal 3, and after the SIFS time, therequest frame is received from terminal 3. After that, the inquiry frameis transmitted also to terminal 4, and after the SIFS time, requestframe 536 is transmitted from terminal 4. There may be candidateterminals other than terminals 1 to 4, and the similar process may becarried out.

When the inquiry to all the candidate terminals is completed, the basestation determines matters required for UL-MU transmission (selection oftarget terminals or the like), generates trigger frame 507 and transmitstrigger frame 507. Configuration of trigger frame 507 and a sequence ofthe transmission of trigger frame 507 and after are similar to the casein FIG. 7 and the explanation will be omitted. In this sequence example,too, the notification field in which the notification information is setmay be provided in the frame transmitted in UL-MU.

In a sequence example in FIG. 14, timing when the base stationdetermines start of the UL-MU transmission (timing when the inquiryphase is started) is not particularly specified, but the base stationcan determine start of the UL-MU transmission in accordance with arequest from the terminal. A sequence example of this case isillustrated in FIG. 15.

One of the terminals belonging to the BSS of the base station (terminal1, here) transmits request frame 521. To be more precise, terminal 1holds data for uplink transmission and acquires the access right inaccordance with CSMA/CA. That is, during the carrier sense time (standbytime) between the DIFS/AIFS[AC] time and a randomly defined backofftime, the carrier sense is carried out, and since a wireless medium isidle, the access right is acquired. It is assumed that the terminals 2to 4 also hold the data for uplink transmission and acquisition of theaccess right is tried, but terminal 1 acquired the access right.

Terminal 1 transmits request frame 521 during TXOP based on the accessright. Request frame 521 only needs to be defined similarly to therequest frame used in the sequence example in FIG. 14. The base stationdetermines start of the UL-MU transmission upon reception of requestframe 521.

The base station selects candidate terminals for UL-MU communicationfrom the terminals other than terminal 1 and transmits inquiry frame 522including information designating the selected candidate terminal. To bemore precise, the base station transmits inquiry frame 522 after theSIFS time from reception of request frame 521. Inquiry frame 522 may beany one of the types of the control frame, management frame, and dataframe. As an example, inquiry frame 522 is a control frame. A value of asubtype may be newly defined for inquiry frame 522. As an example, theRA of inquiry frame 522 is a broadcast address or a multicast address,and the TA is a BSSID or a MAC address of the base station.

A field for designating the candidate terminal is provided in the FrameBody field, the MAC header or the physical header of inquiry frame 522,and information designating the candidate terminal is set in the field.A field storing an identifier of a candidate terminal (may be called aterminal ID field) is provided for the number of candidate terminals,for example, and the identifier of each selected candidate terminal (AIDor MAC address, etc.) is set in each terminal ID field. Alternatively, agroup ID of a group to which each candidate terminal belongs in commonmay be set in the field, and in this case, terminal 1 may belong to thegroup.

The terminal which received inquiry frame 522 confirms that the terminalitself is designated in inquiry frame 522. It determines whether theterminal itself is designated on the basis of whether the identifier ofthe terminal itself is set in any of the terminal ID field or on whetherthe terminal itself belongs to the group with the group ID set in thefield, for example. If the terminal (excluding terminal 1) is designatedas the candidate terminal, the access right is acquired on the basis ofCSMA/CA, and the request frame is transmitted. In the illustratedexample, each of terminals 2 to 4 acquires the access right andtransmits request frames 523, 525, and 527.

When the base station has received the request frames from all thecandidate terminals or when predetermined time has elapsed, it finishesthe inquiry phase. When the base station finishes the inquiry phase, itdetermines matters required for UL-MU (selection of the target terminaland determination of the parameter information, etc.). The base stationacquires the access right the wireless medium on the basis of CSMA/CAand transmits trigger frame 507 generated on the basis of theabove-described determination. Since the sequence of the transmission oftrigger frame 507 and after is similar to the case in FIG. 7, theexplanation will be omitted. In this sequence example, too, thenotification field in which the notification information is set may beprovided in the frame transmitted in UL-MU.

The sequence examples of the inquiry phase illustrated in FIGS. 14 and15 are mere examples, and a sequence other than those illustrated heremay be also used. In the sequence example in FIG. 15, the base stationdoes not return the acknowledgement response frame to request frames523, 525, and 527, for example, but the acknowledgement response framemay be returned. In the sequence example in FIG. 14, the inquiry frameis sequentially transmitted to all the candidate terminals, but it maybe so configured that the base station transmits the inquiry frameincluding information designating a plurality of the candidate terminals(identifier of each candidate terminal or a group ID, etc.) only once atthe first, and the terminal designated by the inquiry frame sequentiallytransmits the request frame at an interval of SIFS time. In this case,this inquiry frame includes information specifying the order of thecandidate terminals to which the request frame is to be transmitted, andsince the order of the terminal itself is grasped from this information,and moreover from the request frame length (the request frame lengthsuch as a fixed length, etc. is assumed to be known in advance), timingof the request frame to be transmitted by the terminal itself may bealso grasped. Alternatively, the order of the terminal itself may beindirectly grasped in accordance with where in the order of the fieldsstoring the identifier in the inquiry frame the terminal itself is set.Various sequence examples can be considered as the inquiry phase otherthan those described here.

Moreover, as a variation of the sequence in FIG. 14 or 15, the terminalsdesignated by the trigger frame can transmit transmission requests byUL-MU in response to the trigger frame. For example, each terminaltransmits QoS Null data and includes the information of the transmissionbuffer (a data amount in the transmission buffer or the like) in the MACheader. In this case, the PPDU length of UL-MU designated by the triggerframe is limited by a maximum length of the MAC header, for example. Inthe trigger frame, information for notifying an intention of collectionof the transmission requests may be set. The terminal designated by thetrigger frame may transmit their transmission buffer information whenthis information is set. Naturally, the PPDU length longer than themaximum length of the MAC header may be designated, and in this case,the frame including the transmission request (transmission bufferinformation or the like) in the MAC header may be transmitted while thedata adjusted to that size is included in the Frame Body field.

As another variation, the transmission buffer information may beincluded in each of the frames to which is transmitted by one or aplurality of terminals performing UL-MU by using a scheme called randomaccess OFDMA which will be described later. At this time, the frame tobe transmitted from the terminal is similar to the case of theabove-described variation. When there is a transmission request, thatis, when there is data for uplink transmission in the transmissionbuffer, the terminal randomly selects a resource block for which theterminal has not been designated (a resource block for which no terminalhas been designated, that is, a resource block which can be used by anarbitrary terminal) by the trigger frame for random access which will bedescribed later and transmits a frame including the transmission requestthrough the selected resource block.

The random access OFDMA will be described. In the random access OFDMA,similarly to the case of the above-described UL-OFDMA, the base stationtransmits the trigger frame, and in response to this trigger frame, oneor a plurality of the terminals simultaneously carries out uplinktransmission. However, this trigger frame does not designate a terminalbut designates only a resource block to be used. However, same terminalmay be designated for some resource blocks while same terminal may notbe designated for the other resource blocks in some cases. In any case,the terminal which received the trigger frame (terminal to which anyresource block has not been designated, for example) selects and usesthe resource block randomly from the resource blocks to which noterminal is designated (resource blocks with no terminal designated).The trigger frame including designation of the resource block with noterminal designated as above is called a trigger frame for random accessin some cases. By using the trigger frame for random access as thetrigger frame transmitted by the base station, the terminals notdesignated by the trigger frame can select the resource blocks randomlyfrom the resource blocks with no terminal designated and can transmitframes. A method by which the terminal selects the resource blockrandomly may be an arbitrary method such as a method of selection byusing random numbers. Configuration of the trigger frame for randomaccess may be arbitrary as long as the resource block with no terminaldesignated can be expressed. In the format in FIG. 11A, for example, itmay be so configured that a predetermined identifier (identifier notassigned to any terminal) and an identifier of the resource block areset instead of the identifier of the terminal in the STA Info field, andthe resource block to which this predetermined identifier is set isinterpreted to be the resource block with no terminal designated.

FIG. 16 illustrates a flowchart of an exemplary operation of a terminalaccording to the embodiment of the present invention. This operation ofthe terminal corresponds to the operation of the terminal in thesequence example illustrated in FIG. 7. When the terminal holds data fortransmission (YES at S101), it acquires the access right to the wirelessmedium in accordance with CSMA/CA, generates a data frame including thedata and transmits the data frame (to be more precise, a physical packetincluding the data frame) during TXOP (S102). Here, the data frame orthe physical header of the physical packet includes the above-describednotification field, and in the notification field, notificationinformation (see the notification information in the above-describedfirst to ninth examples) is set. As described above, the notificationinformation is stored in the data frame to be spontaneously transmittedby the terminal and is sent. That is, it is transmitted withoutreceiving a transmission request for the notification information fromthe base station. In this example, the example in which the notificationinformation is included in the data frame is illustrated, but thenotification information can be included in the management frame or thecontrol frame for transmission. While the terminal does not receive thetrigger frame from the base station (NO at S103), it repeats processingsimilar to the above. When the terminal has received the trigger framefrom the base station (YES at S103), it determines whether the terminalitself is designated as a target terminal of UL-MU transmission and ifthe terminal itself is designated (YES at S104), it transmits the dataframe including data for transmission (to be more precise, a physicalpacket including the data frame) after certain time from completion ofreception of the trigger frame (S105).

When a condition relating to the data to be transmitted or the dataframe or the like is designated by the trigger frame, the data frame isgenerated and transmitted so as to satisfy the condition. When there isno data for transmission, Null Packet may be transmitted or nothing maybe transmitted. Here, the data frame is transmitted, but the managementframe or the control frame may be transmitted. The notification field inwhich the notification information is set may be provided in the dataframe. The terminal receives the acknowledgement response frame from thebase station after SIFS time from the transmission of the data frame.The terminal can be configured to further transmit the data frame afterSIFS from the reception of the acknowledgement response frame.

FIG. 17 illustrates a flowchart of an exemplary operation of the basestation according to the embodiment of the present invention. Thisoperation of the base station corresponds to the operation of the basestation in the sequence example illustrated in FIG. 7. When the basestation receives a frame such as data frame or the like from theterminal (S201), it acquires notification information from the frame (inthe case of a frame with a notification field) and manages a state ofthe terminal such as presence of a request for UL-MU transmission on thebasis of the notification information (S202). The base station repeatsthe above-described processing until it determines start of the UL-MUcommunication. When it determines start of the UL-MU communication (YESat S203), it determines required matters such as a target terminal ofthe UL-MU communication, parameter information at transmission or thelike (S204) and transmits a trigger frame to the target terminal (S205).The base station receives the frame such as the data frame transmittedsimultaneously from the target terminals after certain time from thetransmission of the trigger frame (S206). The base station transmits anacknowledgement response frame to the target terminal after SIFS timefrom the reception of the frame. After that, the base station may returnto processing of determination of required matters (S204) again, mayreturn to the transmission processing of the trigger frame (S205) or mayreturn to the reception processing of the UL-MU transmission (S206).Alternatively, it may return to processing of other steps such as StepS201. When the notification information is set in the frame transmittedin UL-MU from the terminal, the base station uses the notificationinformation for determining the matters required for subsequent andlater UL-MU transmissions.

FIG. 18 illustrates a flowchart of another exemplary operation of thebase station according to the embodiment of the present invention. Adifference from FIG. 17 is that, after the base station determines startof the UL-MU transmission and before transmits the trigger frame, itcarries out an inquiry phase (S207) as illustrated in FIG. 14 or 15. Inthe inquiry phase, candidate terminals carrying out the UL-MUtransmission are selected, and an inquiry frame relating to presence ofa request for carrying out the UL-MU communication or the like istransmitted to the selected candidate terminals on the basis of thenotification information collected before the inquiry phase, forexample. Then, the request frame notifying whether the terminal has arequest for carrying out the UL-MU communication or the like is receivedfrom each of the candidate terminals. In determination of the requiredmatters after the inquiry phase (S204), the target terminals areselected from the terminals having notified presence of a request forcarrying out the UL-MU communication among the candidate terminals, forexample. That is, it can be considered that rough estimation is made bythe notification information collected before the inquiry phase, andestimation with higher accuracy is made by the inquiry during theinquiry phase. After the UL-MU transmission is carried out, it mayreturn to the inquiry phase again or may return to processing of othersteps.

In this embodiment, the notification information is transmitted fordetermining the required matters of the UL-MU communication but as avariation, it can be so configured that, in an HCCA environment, inorder to determine a terminal which becomes a communication target ofthe base station or to determine TID for data transmission by theterminal, the notification information is transmitted from each terminalto the base station. In the HCCA environment, the base station transmitsQoS CF-Poll frame to the terminal, and the terminal is allowed totransmit a frame during TXOP designated by the frame. TID is designatedin the QoS CF-Poll frame. Thus, as a basis for determination of the basestation to designate at least either one of the terminal or TID, eachterminal can transmit the notification information according to at leastone of the above-described first to ninth examples or an arbitrarycombination of them.

As described above, according to this embodiment, the base station canefficiently collect notification information by transmitting a frameincluding notification information without reception of a request fromthe base station by each terminal. Moreover, by including thenotification information in a frame (data frame, association requestframe, etc.) to be single-user transmitted to the base station normallyon the CSMA/CA basis, the base station can collect the notificationinformation while each terminal suppresses lowering of systemefficiency. Moreover, the base station can narrow down the terminalshaving data for uplink more reliably by providing the inquiry phase.

Second Embodiment

FIG. 19 is a functional block diagram of a base station (access point)400 according to the second embodiment. The access point includes acommunication processor 401, a transmitter 402, a receiver 403, antennas42A, 42B, 42C, and 42D, a network processor 404, a wired I/F 405, and amemory 406. The access point 400 is connected to a server 407 throughthe wired I/F 405. The communication processor 401 has functions similarto MAC processor 10 and MAC/PHY manager 60 in the first embodiment. Thetransmitter 402 and the receiver 403 have functions similar to PHYprocessor 50 and analog processor 70 in the first embodiment. Thecommunication processor 404 has functions similar to upper layerprocessor 90 in the first embodiment. The communication processor 401may internally possess a buffer for transferring data to and from thenetwork processor 404. The buffer may be a volatile memory, such as anSRAM or a DRAM, or may be a non-volatile memory, such as a NAND or anMRAM.

The network processor 404 controls data exchange with the communicationprocessor 401, data writing and reading to and from the memory 406, andcommunication with the server 407 through the wired I/F 405. The networkprocessor 404 may execute a higher communication process of the MAClayer, such as TCP/IP or UDP/IP, or a process of the application layer.The operation of the network processor may be performed throughprocessing of software (program) by a processor, such as a CPU. Theoperation may be performed by hardware or may be performed by both ofthe software and the hardware.

For example, the communication processor 401 corresponds to a basebandintegrated circuit, and the transmitter 402 and the receiver 403correspond to an RF integrated circuit that transmits and receivesframes. The communication processor 401 and the network processor 404may be formed by one integrated circuit (one chip). Parts that executeprocessing of digital areas of the transmitter 402 and the receiver 403and parts that execute processing of analog areas may be formed bydifferent chips. The communication processor 401 may execute a highercommunication process of the MAC layer, such as TCP/IP or UDP/IP.Although the number of antennas is four here, it is only necessary thatat least one antenna is included.

The memory 406 saves data received from the server 407 and data receivedby the receiver 402. The memory 406 may be, for example, a volatilememory, such as a DRAM, or may be a non-volatile memory, such as a NANDor an MRAM. The memory 406 may be an SSD, an HDD, an SD card, an eMMC,or the like. The memory 406 may be provided outside of the base station400.

The wired I/F 405 transmits and receives data to and from the server407. Although the communication with the server 407 is performed througha wire in the present embodiment, the communication with the server 407may be performed wirelessly.

The server 407 is a communication device that returns a responseincluding requested data in response to reception of a data forwardrequest for requesting transmission of the data. Examples of the server407 include an HTTP server (Web server) and an FTP server. However, theserver 407 is not limited to these as long as the server 407 has afunction of returning the requested data. The server 407 may be acommunication device operated by the user, such as a PC or a smartphone.The server 407 may wirelessly communicate with the base station 400.

When the STA belonging to the BSS of the base station 400 issues aforward request of data for the server 407, a packet regarding the dataforward request is transmitted to the base station 400. The base station400 receives the packet through the antennas 42A to 42D. The basestation 400 causes the receiver 403 to execute the process of thephysical layer and the like and causes the communication processor 401to execute the process of the MAC layer and the like.

The network processor 404 analyzes the packet received from thecommunication processor 401. Specifically, the network processor 404checks the destination IP address, the destination port number, and thelike. When the data of the packet is a data forward request such as anHTTP GET request, the network processor 404 checks whether the datarequested by the data forward request (for example, data in the URLrequested by the HTTP GET request) is cached (stored) in the memory 406.A table associating the URL (or reduced expression of the URL, such as ahash value or an identifier substituting the URL) and the data is storedin the memory 406. The fact that the data is cached in the memory 406will be expressed that the cache data exists in the memory 406.

When the cache data does not exist in the memory 406, the networkprocessor 404 transmits the data forward request to the server 407through the wired I/F 405. In other words, the network processor 404substitutes the STA to transmit the data forward request to the server407. Specifically, the network processor 404 generates an HTTP requestand executes protocol processing, such as adding the TCP/IP header, totransfer the packet to the wired I/F 405. The wired I/F 405 transmitsthe received packet to the server 407.

The wired I/F 405 receives, from the server 407, a packet that is aresponse to the data forward request. From the IP header of the packetreceived through the wired I/F 405, the network processor 404 figuresout that the packet is addressed to the STA and transfers the packet tothe communication processor 401. The communication processor 401executes processing of the MAC layer and the like for the packet. Thetransmitter 402 executes processing of the physical layer and the likeand transmits the packet addressed to the STA from the antennas 42A to42D. The network processor 404 associates the data received from theserver 407 with the URL (or reduced expression of the URL) and saves thecache data in the memory 406.

When the cache data exists in the memory 406, the network processor 404reads the data requested by the data forward request from the memory 406and transmits the data to the communication processor 401. Specifically,the network processor 404 adds the HTTP header or the like to the dataread from the memory 406 and executes protocol processing, such asadding the TCP/IP header, to transmit the packet to the communicationprocessor 401. In this case, the transmitter IP address of the packet isset to the same IP address as the server, and the transmitter portnumber is also set to the same port number as the server (destinationport number of the packet transmitted by the communication terminal),for example. Therefore, it can be viewed from the STA as ifcommunication with the server 407 is established. The communicationprocessor 401 executes processing of the MAC layer and the like for thepacket. The transmitter 402 executes processing of the physical layerand the like and transmits the packet addressed to the STA from theantennas 42A to 42D.

According to the operation, frequently accessed data is responded basedon the cache data saved in the memory 406, and the traffic between theserver 407 and the base station 400 can be reduced. Note that theoperation of the network processor 404 is not limited to the operationof the present embodiment. There is no problem in performing otheroperation when a general caching proxy is used, in which data isacquired from the server 407 in place of the STA, the data is cached inthe memory 406, and a response is made from the cache data of the memory406 for a data forward request of the same data.

A terminal (STA) with the cache function can also be realized by thesame block configuration as FIG. 19. In this case, the wired I/F 405 maybe omitted. The terminal according to the present embodiment can appliedas the terminal in the first embodiment. For example, the terminal readsout the data cached in the memory 406 and transmits a data frameincluding the read data (specifically, a physical packet having aphysical header added) to the base station. The data may be dataacquired from the server 407 or data acquired in another method (dataacquired from another external device or user-specified file data etc.).The terminal may generate notification information (control information)in each example in the first embodiment based on data for transmissionto the base station, cached in the memory 406. The terminal may transmitthe data for transmission to the base station, cached in the memory 406by any of data frame 501, 503 and 505 or any of data frames 509 to 512in FIG. 7. The terminal may transmit the generated notificationinformation by any of data frame 501, 503 and 505, or any of data frames509 to 512 by uplink multi-user transmission in FIG. 7

In the case of the multi-hop network, the terminal has a role of anon-base station terminal and a role of a base station. When theterminal operates as the base station, the terminal transfers datahaving received from another terminal to another base station, and forthis reason, the terminal may cache the received data in the memory.

The base station according to the present invention can be applied forthe base station in the first embodiment. In this case, the followingoperation can be carried out. The base station reads out the data fortransmission to a terminal from the memory 406 and generates andtransmits a frame including the read data (a trigger frame, an inquiryframe or data frame etc.). The base station may add data fortransmission each terminal in the memory 406 to a frame such as thetrigger frame. The data for transmission each terminal in the memory 406is not limited to data acquired based on a data transfer request fromeach terminal and may be data transmitted from the server 407 or anexternal device except the server 407 regardless the data transferrequest. For example, the data may be push data addressed to eachterminal or e-mail data. The base station may transmit data fortransmission to a plurality of terminals in the memory 406 by downlinkmulti-user scheme (DL-OFDMA, DL-MU-MIMO or a combination thereof (suchas DL-OFDMA & DL-MU-MIMO).

Third Embodiment

FIG. 20 shows an example of entire configuration of a terminal or a basestation. The example of configuration is just an example, and thepresent embodiment is not limited to this. The terminal or the basestation includes one or a plurality of antennas 1 to n (n is an integerequal to or greater than 1), a wireless LAN module 148, and a hostsystem 149. The wireless LAN module 148 corresponds to the wirelesscommunication device according to the first embodiment. The wireless LANmodule 148 includes a host interface and is connected to the host system149 through the host interface. Other than the connection to the hostsystem 149 through the connection cable, the wireless LAN module 148 maybe directly connected to the host system 149. The wireless LAN module148 can be mounted on a substrate by soldering or the like and can beconnected to the host system 149 through wiring of the substrate. Thehost system 149 uses the wireless LAN module 148 and the antennas 1 to nto communicate with external apparatuses according to an arbitrarycommunication protocol. The communication protocol may include theTCP/IP and a protocol of a layer higher than that. Alternatively, theTCP/IP may be mounted on the wireless LAN module 148, and the hostsystem 149 may execute only a protocol in a layer higher than that. Inthis case, the configuration of the host system 149 can be simplified.Examples of the present terminal include a mobile terminal, a TV, adigital camera, a wearable device, a tablet, a smartphone, a gamedevice, a network storage device, a monitor, a digital audio player, aWeb camera, a video camera, a projector, a navigation system, anexternal adaptor, an internal adaptor, a set top box, a gateway, aprinter server, a mobile access point, a router, an enterprise/serviceprovider access point, a portable device, a hand-held device and so on.

FIG. 21 shows an example of hardware configuration of a WLAN module. Theconfiguration shown in the figure may be applied for each case in wherethe wireless communication device is mounted in non-AP terminal or in AP(Access Point) provided correspondingly to each function. That is, theconfiguration can be applied as specific examples of the wirelesscommunication device in FIG. 1. In the configuration shown in figure, atleast one antenna is included although a plurality of antennas areincluded. In this case, a plurality of sets of a transmission system(216 and 222 to 225), a reception system (217, 232 to 235), a PLL 242, acrystal oscillator (reference signal source) 243, and a switch 245 maybe arranged according to the antennas, and each set may be connected toa control circuit 212. One or both of the PLL 242 and the crystaloscillator 243 correspond to an oscillator according to the presentembodiment.

The wireless LAN module (wireless communication device) includes abaseband IC (Integrated Circuit) 211, an RF (Radio Frequency) IC 221, abalun 225, the switch 245, and the antenna 247.

The baseband IC 211 includes the baseband circuit (control circuit) 212,a memory 213, a host interface 214, a CPU 215, a DAC (Digital to AnalogConverter) 216, and an ADC (Analog to Digital Converter) 217.

The baseband IC 211 and the RF IC 221 may be formed on the samesubstrate. The baseband IC 211 and the RF IC 221 may be formed by onechip. Both or one of the DAC 216 and the ADC 217 may be arranged on theRF IC 221 or may be arranged on another IC. Both or one of the memory213 and the CPU 215 may be arranged on an IC other than the baseband IC.

The memory 213 stores data to be transferred to and from the hostsystem. The memory 213 also stores one or both of information to betransmitted to the terminal or the base station and informationtransmitted from the terminal or the base station. The memory 213 mayalso store a program necessary for the execution of the CPU 215 and maybe used as a work area for the CPU 215 to execute the program. Thememory 213 may be a volatile memory, such as an SRAM or a DRAM, or maybe a non-volatile memory, such as a NAND or an MRAM.

The host interface 214 is an interface for connection to the hostsystem. The interface can be anything, such as UART, SPI, SDIO, USB, orPCI Express.

The CPU 215 is a processor that executes a program to control thebaseband circuit 212. The baseband circuit 212 mainly executes a processof the MAC layer and a process of the physical layer. One or both of thebaseband circuit 212 and the CPU 215 correspond to the communicationcontrol apparatus that controls communication, the controller thatcontrols communication, or controlling circuitry that controlscommunication.

At least one of the baseband circuit 212 or the CPU 215 may include aclock generator that generates a clock and may manage internal time bythe clock generated by the clock generator.

For the process of the physical layer, the baseband circuit 212 performsaddition of the physical header, coding, encryption, modulation process(which may include MIMO modulation), and the like of the frame to betransmitted and generates, for example, two types of digital basebandsignals (hereinafter, “digital I signal” and “digital Q signal”).

The DAC 216 performs DA conversion of signals input from the basebandcircuit 212. More specifically, the DAC 216 converts the digital Isignal to an analog I signal and converts the digital Q signal to ananalog Q signal. Note that a single system signal may be transmittedwithout performing quadrature modulation. When a plurality of antennasare included, and single system or multi-system transmission signalsequivalent to the number of antennas are to be distributed andtransmitted, the number of provided DACs and the like may correspond tothe number of antennas.

The RF IC 221 is, for example, one or both of an RF analog IC and a highfrequency IC. The RF IC 221 includes a filter 222, a mixer 223, apreamplifier (PA) 224, the PLL (Phase Locked Loop) 242, a low noiseamplifier (LNA) 234, a balun 235, a mixer 233, and a filter 232. Some ofthe elements may be arranged on the baseband IC 211 or another IC. Thefilters 222 and 232 may be bandpass filters or low pass filters.

The filter 222 extracts a signal of a desired band from each of theanalog I signal and the analog Q signal input from the DAC 216. The PLL242 uses an oscillation signal input from the crystal oscillator 243 andperforms one or both of division and multiplication of the oscillationsignal to thereby generate a signal at a certain frequency synchronizedwith the phase of the input signal. Note that the PLL 242 includes a VCO(Voltage Controlled Oscillator) and uses the VCO to perform feedbackcontrol based on the oscillation signal input from the crystaloscillator 243 to thereby obtain the signal at the certain frequency.The generated signal at the certain frequency is input to the mixer 223and the mixer 233. The PLL 242 is equivalent to an example of anoscillator that generates a signal at a certain frequency.

The mixer 223 uses the signal at the certain frequency supplied from thePLL 242 to up-convert the analog I signal and the analog Q signal passedthrough the filter 222 into a radio frequency. The preamplifier (PA)amplifies the analog I signal and the analog Q signal at the radiofrequency generated by the mixer 223, up to desired output power. Thebalun 225 is a converter for converting a balanced signal (differentialsignal) to an unbalanced signal (single-ended signal). Although thebalanced signal is handled by the RF IC 221, the unbalanced signal ishandled from the output of the RF IC 221 to the antenna 247. Therefore,the balun 225 performs the signal conversions.

The switch 245 is connected to the balun 225 on the transmission sideduring the transmission and is connected to the LNA 234 or the RF IC 221on the reception side during the reception. The baseband IC 211 or theRF IC 221 may control the switch 245. There may be another circuit thatcontrols the switch 245, and the circuit may control the switch 245.

The analog I signal and the analog Q signal at the radio frequencyamplified by the preamplifier 224 are subjected to balanced-unbalancedconversion by the balun 225 and are then emitted as radio waves to thespace from the antenna 247.

The antenna 247 may be a chip antenna, may be an antenna formed bywiring on a printed circuit board, or may be an antenna formed by usinga linear conductive element.

The LNA 234 in the RF IC 221 amplifies a signal received from theantenna 247 through the switch 245 up to a level that allowsdemodulation, while maintaining the noise low. The balun 235 performsunbalanced-balanced conversion of the signal amplified by the low noiseamplifier (LNA) 234. The mixer 233 uses the signal at the certainfrequency input from the PLL 242 to down-convert, to a baseband, thereception signal converted to a balanced signal by the balun 235. Morespecifically, the mixer 233 includes a unit that generates carrier wavesshifted by a phase of 90 degrees based on the signal at the certainfrequency input from the PLL 242. The mixer 233 uses the carrier wavesshifted by a phase of 90 degrees to perform quadrature demodulation ofthe reception signal converted by the balun 235 and generates an I(In-phase) signal with the same phase as the reception signal and a Q(Quad-phase) signal with the phase delayed by 90 degrees. The filter 232extracts signals with desired frequency components from the I signal andthe Q signal. Gains of the I signal and the Q signal extracted by thefilter 232 are adjusted, and the I signal and the Q signal are outputfrom the RF IC 221.

The ADC 217 in the baseband IC 211 performs AD conversion of the inputsignal from the RF IC 221. More specifically, the ADC 217 converts the Isignal to a digital I signal and converts the Q signal to a digital Qsignal. Note that a single system signal may be received withoutperforming quadrature demodulation.

When a plurality of antennas are provided, the number of provided ADCsmay correspond to the number of antennas. Based on the digital I signaland the digital Q signal, the baseband circuit 212 executes a process ofthe physical layer and the like, such as demodulation process, errorcorrecting code process, and process of physical header, and obtains aframe. The baseband circuit 212 applies a process of the MAC layer tothe frame. Note that the baseband circuit 212 may be configured toexecute a process of TCP/IP when the TCP/IP is implemented.

Fourth Embodiment

FIG. 22A and FIG. 22B are perspective views of wireless terminalaccording to the present embodiment. The wireless terminal in FIG. 22Ais a notebook PC 301 and the wireless communication device (or awireless device) in FIG. 22B is a mobile terminal 321. Each of themcorresponds to one form of a terminal (which may indicate a basestation). The notebook PC 301 and the mobile terminal 321 are equippedwith wireless communication devices 305 and 315, respectively. Thewireless communication device provided in a terminal (which may indicatea base station) which has been described above can be used as thewireless communication devices 305 and 315. A wireless terminal carryinga wireless communication device is not limited to notebook PCs andmobile terminals. For example, it can be installed in a TV, a digitalcamera, a wearable device, a tablet, a smart phone, a gaming device, anetwork storage device, a monitor, a digital audio player, a web camera,a video camera, a projector, a navigation system, an external adapter,an internal adapter, a set top box, a gateway, a printer server, amobile access point, a router, an enterprise/service provider accesspoint, a portable device, a handheld device and so on.

Moreover, a wireless communication device installed in a terminal (whichmay indicate a base station) can also be provided in a memory card. FIG.23 illustrates an example of a wireless communication device mounted ona memory card. A memory card 331 contains a wireless communicationdevice 355 and a body case 332. The memory card 331 uses the wirelesscommunication device 355 for wireless communication with externaldevices. Here, in FIG. 23, the description of other installed elements(for example, a memory, and so on) in the memory card 331 is omitted.

Fifth Embodiment

In the present embodiment, a bus, a processor unit and an externalinterface unit are provided in addition to the configuration of thewireless communication device according to any of the above embodiments.The processor unit and the external interface unit are connected with anexternal memory (a buffer) through the bus. A firmware operates theprocessor unit. Thus, by adopting a configuration in which the firmwareis included in the wireless communication device, the functions of thewireless communication device can be easily changed by rewriting thefirmware. The processing unit in which the firmware operates may be aprocessor that performs the process of the communication controllingdevice or the control unit according to the present embodiment, or maybe another processor that performs a process relating to extending oraltering the functions of the process of the communication controllingdevice or the control unit. The processing unit in which the firmwareoperates may be included in the access point or the wireless terminalaccording to the present embodiment. Alternatively, the processing unitmay be included in the integrated circuit of the wireless communicationdevice installed in the access point, or in the integrated circuit ofthe wireless communication device installed in the wireless terminal.

Sixth Embodiment

In the present embodiment, a clock generating unit is provided inaddition to the configuration of the wireless communication deviceaccording to any of the above embodiments. The clock generating unitgenerates a clock and outputs the clock from an output terminal to theexterior of the wireless communication device. Thus, by outputting tothe exterior the clock generated inside the wireless communicationdevice and operating the host by the clock output to the exterior, it ispossible to operate the host and the wireless communication device in asynchronized manner.

Seventh Embodiment

In the present embodiment, a power source unit, a power sourcecontrolling unit and a wireless power feeding unit are included inaddition to the configuration of the wireless communication deviceaccording to any of the above embodiments. The power supply controllingunit is connected to the power source unit and to the wireless powerfeeding unit, and performs control to select a power source to besupplied to the wireless communication device. Thus, by adopting aconfiguration in which the power source is included in the wirelesscommunication device, power consumption reduction operations thatcontrol the power source are possible.

Eighth Embodiment

In the present embodiment, a SIM card is added to the configuration ofthe wireless communication device according to any of the aboveembodiments. For example, the SIM card is connected with MAC processor10, MAC/PHY manager 60, or a controller in the wireless communicationdevice. Thus, by adopting a configuration in which the SIM card isincluded in the wireless communication device, authentication processingcan be easily performed.

Ninth Embodiment

In the eighth embodiment, a video image compressing/decompressing unitis added to the configuration of the wireless communication deviceaccording to any of the above embodiments. The video imagecompressing/decompressing unit is connected to the bus. Thus, byadopting a configuration in which the video imagecompressing/decompressing unit is included in the wireless communicationdevice, transmitting a compressed video image and decompressing areceived compressed video image can be easily done.

Tenth Embodiment

In the present embodiment, an LED unit is added to the configuration ofthe wireless communication device according to any of the aboveembodiments. For example, the LED unit is connected to at least one ofMAC processor 10, MAC/PHY manager 60, a transmission processing circuit,a reception processing circuit or a controller in the wirelesscommunication device. Thus, by adopting a configuration in which the LEDunit is included in the wireless communication device, notifying theoperation state of the wireless communication device to the user can beeasily done.

Eleventh Embodiment

In the present embodiment, a vibrator unit is included in addition tothe configuration of the wireless communication device wirelesscommunication device according to any of the above embodiments. Forexample, the vibrator unit is connected to at least one of MAC processor10, MAC/PHY manager 60, a transmission processing circuit, a receptionprocessing circuit or a controller in the wireless communication device.Thus, by adopting a configuration in which the vibrator unit is includedin the wireless communication device, notifying the operation state ofthe wireless communication device to the user can be easily done.

Twelfth embodiment

In the present embodiment, the configuration of the wirelesscommunication device includes a display in addition to the configurationof the wireless communication device (the wireless communication deviceof the terminal (which may indicate the base station)) according to anyone of the above embodiments. The display may be connected to the MACprocessor in the wireless communication device via a bus (not shown). Asseen from the above, the configuration including the display to displaythe operation state of the wireless communication device on the displayallows the operation status of the wireless communication device to beeasily notified to a user.

Thirteenth Embodiment

In the present embodiment, [1] the frame type in the wirelesscommunication system, [2] a technique of disconnection between wirelesscommunication devices, [3] an access scheme of a wireless LAN system and[4] a frame interval of a wireless LAN are described.

[1] Frame Type in Communication System

Generally, as mentioned above, frames treated on a wireless accessprotocol in a wireless communication system are roughly divided intothree types of the data frame, the management frame and the controlframe. These types are normally shown in a header part which is commonlyprovided to frames. As a display method of the frame type, three typesmay be distinguished in one field or may be distinguished by acombination of two fields. In IEEE 802.11 standard, identification of aframe type is made based on two fields of Type and Subtype in the FrameControl field in the header part of the MAC frame. The Type field is onefor generally classifying frames into a data frame, a management frame,or a control frame and the Subtype field is one for identifying moredetailed type in each of the classified frame types such as a beaconframe belonging to the management frame.

The management frame is a frame used to manage a physical communicationlink with a different wireless communication device. For example, thereare a frame used to perform communication setting with the differentwireless communication device or a frame to release communication link(that is, to disconnect the connection), and a frame related to thepower save operation in the wireless communication device.

The data frame is a frame to transmit data generated in the wirelesscommunication device to the different wireless communication deviceafter a physical communication link with the different wirelesscommunication device is established. The data is generated in a higherlayer of the present embodiment and generated by, for example, a user'soperation.

The control frame is a frame used to perform control at the time oftransmission and reception (exchange) of the data frame with thedifferent wireless communication device. A response frame transmittedfor the acknowledgment in a case where the wireless communication devicereceives the data frame or the management frame, belongs to the controlframe. The response frame is, for example, an ACK frame or a BlockACKframe. The RTS frame and the CTS frame are also the control frame.

These three types of frames are subjected to processing based on thenecessity in the physical layer and then transmitted as physical packetsvia an antenna. In IEEE 802.11 standard (including the extended standardsuch as IEEE Std 802.11ac-2013), an association process is defined asone procedure for connection establishment. The association requestframe and the association response frame which are used in the procedureare a management frame. Since the association request frame and theassociation response frame is the management frame transmitted in aunicast scheme, the frames causes the wireless communication terminal inthe receiving side to transmit an ACK frame being a response frame. TheACK frame is a control frame as described in the above.

[2] Technique of Disconnection Between Wireless Communication Devices

For disconnection of the connection (release), there are an explicittechnique and an implicit technique. As the explicit technique, a frameto disconnect any one of the connected wireless communication devices istransmitted. This frame corresponds to Deauthentication frame defined inIEEE 802.11 standard and is classified into the management frame.Normally, it is determined that the connection is disconnected at thetiming of transmitting the frame to disconnect the connection in awireless communication device on the side to transmit the frame and atthe timing of receiving the frame to disconnect the connection in awireless communication device on the side to receive the frame.Afterward, it returns to the initial state in a communication phase, forexample, a state to search for a wireless communication device of thecommunicating partner. In a case that the wireless communication basestation disconnects with a wireless communication terminal, for example,the base station deletes information on the wireless communicationdevice from a connection management table if the base station holds theconnection management table for managing wireless communicationterminals which entries into the BSS of the base station-self. Forexample, in a case that the base station assigns an AID to each wirelesscommunication terminal which entries into the BSS at the time when thebase station permitted each wireless communication terminal to connectto the base station-self in the association process, the base stationdeletes the held information related to the AID of the wirelesscommunication terminal disconnected with the base station and mayrelease the AID to assign it to another wireless communication devicewhich newly entries into the BSS.

On the other hand, as the implicit technique, it is determined that theconnection state is disconnected in a case where frame transmission(transmission of a data frame and management frame or transmission of aresponse frame with respect to a frame transmitted by the subjectdevice) is not detected from a wireless communication device of theconnection partner which has established the connection for a certainperiod. Such a technique is provided because, in a state where it isdetermined that the connection is disconnected as mentioned above, astate is considered where the physical wireless link cannot be secured,for example, the communication distance to the wireless communicationdevice of the connection destination is separated and the radio signalscannot be received or decoded. That is, it is because the reception ofthe frame to disconnect the connection cannot be expected.

As a specific example to determine the disconnection of connection in animplicit method, a timer is used. For example, at the time oftransmitting a data frame that requests an acknowledgment responseframe, a first timer (for example, a retransmission timer for a dataframe) that limits the retransmission period of the frame is activated,and, if the acknowledgement response frame to the frame is not receiveduntil the expiration of the first timer (that is, until a desiredretransmission period passes), retransmission is performed. When theacknowledgment response frame to the frame is received, the first timeris stopped.

On the other hand, when the acknowledgment response frame is notreceived and the first timer expires, for example, a management frame toconfirm whether a wireless communication device of a connection partneris still present (in a communication range) (in other words, whether awireless link is secured) is transmitted, and, at the same time, asecond timer (for example, a retransmission timer for the managementframe) to limit the retransmission period of the frame is activated.Similarly to the first timer, even in the second timer, retransmissionis performed if an acknowledgment response frame to the frame is notreceived until the second timer expires, and it is determined that theconnection is disconnected when the second timer expires.

Alternatively, a third timer is activated when a frame is received froma wireless communication device of the connection partner, the thirdtimer is stopped every time the frame is newly received from thewireless communication device of the connection partner, and it isactivated from the initial value again. When the third timer expires,similarly to the above, a management frame to confirm whether thewireless communication device of the connection party is still present(in a communication range) (in other words, whether a wireless link issecured) is transmitted, and, at the same time, a second timer (forexample, a retransmission timer for the management frame) to limit theretransmission period of the frame is activated. Even in this case,retransmission is performed if an acknowledgment response frame to theframe is not received until the second timer expires, and it isdetermined that the connection is disconnected when the second timerexpires. The latter management frame to confirm whether the wirelesscommunication device of the connection partner is still present maydiffer from the management frame in the former case. Moreover, regardingthe timer to limit the retransmission of the management frame in thelatter case, although the same one as that in the former case is used asthe second timer, a different timer may be used.

[3] Access Scheme of Wireless LAN System

For example, there is a wireless LAN system with an assumption ofcommunication or competition with a plurality of wireless communicationdevices. CSMA/CA is set as the basis of an access scheme in IEEE 802.11(including an extension standard or the like) wireless LAN. In a schemein which transmission by a certain wireless communication device isgrasped and transmission is performed after a fixed time from thetransmission end, simultaneous transmission is performed in theplurality of wireless communication devices that grasp the transmissionby the wireless communication device, and, as a result, radio signalscollide and frame transmission fails. By grasping the transmission bythe certain wireless communication device and waiting for a random timefrom the transmission end, transmission by the plurality of wirelesscommunication devices that grasp the transmission by the wirelesscommunication device stochastically disperses. Therefore, if the numberof wireless communication devices in which the earliest time in a randomtime is subtracted is one, frame transmission by the wirelesscommunication device succeeds and it is possible to prevent framecollision. Since the acquisition of the transmission right based on therandom value becomes impartial between the plurality of wirelesscommunication devices, it can say that a scheme adopting CollisionAvoidance is a suitable scheme to share a radio medium between theplurality of wireless communication devices.

[4] Frame Interval of Wireless LAN

The frame interval of IEEE802.11wireless LAN is described. There are sixtypes of frame intervals used in IEEE802.11 wireless LAN, such asdistributed coordination function interframe space (DIFS), arbitrationinterframe space (AIFS), point coordination function interframe space(PIFS), short interframe space (SIFS), extended interframe space (EIFS)and reduced interframe space (RIFS).

The definition of the frame interval is defined as a continuous periodthat should confirm and open the carrier sensing idle beforetransmission in IEEE802.11 wireless LAN, and a strict period from aprevious frame is not discussed. Therefore, the definition is followedin the explanation of IEEE802.11 wireless LAN system. In IEEE802.11wireless LAN, a waiting time at the time of random access based onCSMA/CA is assumed to be the sum of a fixed time and a random time, andit can say that such a definition is made to clarify the fixed time.

DIFS and AIFS are frame intervals used when trying the frame exchangestart in a contention period that competes with other wirelesscommunication devices on the basis of CSMA/CA. DIFS is used in a casewhere priority according to the traffic type is not distinguished, AIFSis used in a case where priority by traffic identifier (TID) isprovided.

Since operation is similar between DIFS and AIFS, an explanation belowwill mainly use AIFS. In IEEE802.11 wireless LAN, access controlincluding the start of frame exchange in the MAC layer is performed. Inaddition, in a case where QoS (Quality of Service) is supported whendata is transferred from a higher layer, the traffic type is notifiedtogether with the data, and the data is classified for the priority atthe time of access on the basis of the traffic type. The class at thetime of this access is referred to as “access category (AC)”. Therefore,the value of AIFS is provided every access category.

PIFS denotes a frame interval to enable access which is morepreferential than other competing wireless communication devices, andthe period is shorter than the values of DIFS and AIFS. SIFS denotes aframe interval which can be used in a case where frame exchangecontinues in a burst manner at the time of transmission of a controlframe of a response system or after the access right is acquired once.EIFS denotes a frame interval caused when frame reception fails (whenthe received frame is determined to be error).

RIFS denotes a frame interval which can be used in a case where aplurality of frames are consecutively transmitted to the same wirelesscommunication device in a burst manner after the access right isacquired once, and a response frame from a wireless communication deviceof the transmission partner is not requested while RIFS is used.

Here, FIG. 24 illustrates one example of frame exchange in a competitiveperiod based on the random access in IEEE802.11 wireless LAN.

When a transmission request of a data frame (W_DATA1) is generated in acertain wireless communication device, a case is assumed where it isrecognized that a medium is busy (busy medium) as a result of carriersensing. In this case, AIFS of a fixed time is set from the time pointat which the carrier sensing becomes idle, and, when a random time(random backoff) is set afterward, data frame W_DATA1 is transmitted tothe communicating partner.

The random time is acquired by multiplying a slot time by a pseudorandominteger led from uniform distribution between contention windows (CW)given by integers from 0. Here, what multiplies CW by the slot time isreferred to as “CW time width”. The initial value of CW is given byCWmin, and the value of CW is increased up to CWmax everyretransmission. Similarly to AIFS, both CWmin and CWmax have valuesevery access category. In a wireless communication device oftransmission destination of W_DATA1, when reception of the data framesucceeds, a response frame (W_ACK1) is transmitted after SIFS from thereception end time point. If it is within a transmission burst timelimit when W_ACK1 is received, the wireless communication device thattransmits W_DATA1 can transmit the next frame (for example, W_DATA2)after SIFS.

Although AIFS, DIFS, PIFS and EIFS are functions between SIFS and theslot-time, SIFS and the slot time are defined every physical layer.Moreover, although parameters whose values being set according to eachaccess category, such as AIFS, CWmin and CWmax, can be set independentlyby a communication group (which is a basic service set (BSS) inIEEE802.11 wireless LAN), the default values are defined.

For example, in the definition of 802.11ac, with an assumption that SIFSis 16 μs and the slot time is 9 μs, and thereby PIFS is 25 μs, DIFS is34 μs, the default value of the frame interval of an access category ofBACKGROUND (AC_BK) in AIFS is 79 μs, the default value of the frameinterval of BEST EFFORT (AC_BE) is 43 μs, the default value of the frameinterval between VIDEO(AC_VI) and VOICE(AC_VO) is 34 μs, and the defaultvalues of CWmin and CWmax are 31 and 1023 in AC_BK and AC_BE, 15 and 31in AC_VI and 7 and 15 in AC_VO. Here, EIFS denotes the sum of SIFS,DIFS, and the time length of a response frame transmitted at the lowestmandatory physical rate. In the wireless communication device which caneffectively takes EIFS, it may estimate an occupation time length of aPHY packet conveying a response frame directed to a PHY packet due towhich the EIFS is caused and calculates a sum of SIFS, DIFS and theestimated time to take the EIFS.

The terms used in each embodiment should be interpreted broadly. Forexample, the term “processor” may encompass a general purpose processor,a central processing unit (CPU), a microprocessor, a digital signalprocessor (DSP), a controller, a microcontroller, a state machine, andso on. According to circumstances, a “processor” may refer to anapplication specific integrated circuit (ASIC), a field programmablegate array (FPGA), and a programmable logic device (PLD), etc. The term“processor” may refer to a combination of processing devices such as aplurality of microprocessors, a combination of a DSP and amicroprocessor, or one or more microprocessors in conjunction with a DSPcore.

As another example, the term “memory” may encompass any electroniccomponent which can store electronic information. The “memory” may referto various types of media such as a random access memory (RAM), aread-only memory (ROM), a programmable read-only memory (PROM), anerasable programmable read only memory (EPROM), an electrically erasablePROM (EEPROM), a non-volatile random access memory (NVRAM), a flashmemory, and a magnetic or optical data storage, which are readable by aprocessor. It can be said that the memory electronically communicateswith a processor if the processor read and/or write information for thememory. The memory may be arranged within a processor and also in thiscase, it can be said that the memory electronically communication withthe processor.

Note that the frames described in the embodiments may indicate not onlythings called frames in, for example, the IEEE 802.11 standard, but alsothings called packets, such as Null Data Packets. When it is expressedthat the base station transmits or receives a plurality of frames or aplurality of X-th frames, the frames or the X-th frames may be the same(for example, the same type or the same content) or may be different. Anarbitrary value can be put into X according to the situation.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions.

1. A wireless communication device, comprising: a receiver configured toreceive a plurality of first frames each including first informationrequired for uplink multi-user transmission; and a transmitterconfigured to transmit a second frame generated on the basis of thefirst information included in the plurality of first frames wherein thetransmitter does not transmit a transmission request for the firstinformation before the first frames are received, and the second frameis a frame instructing transmission of a third frame including dataafter a predetermined time from reception of the second frame. 2.-20.(canceled)